Automotive air conditioning training manual

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Automotive air conditioning training manual

  1. 1. AutomotiveAir Conditioning Training Manual
  2. 2. (I) Theory The four major function..........................................................................................3 Understanding heat................................................................................................4 Change of state......................................................................................................7 Pressure & temperature relationship......................................................................8 The Ozone Layer....................................................................................................9 R134a properties................................................................................................... 10 Principles of air conditioning.................................................................................. 12 (II) System types Expansion block valve system...............................................................................13 Parallel flow condenser system............................................................................. 14 Orifice tube system................................................................................................ 15 Expansion valve dual system.................................................................................16 (III) Components Compressors..........................................................................................................17 Clutches.................................................................................................................22 Lubrication............................................................................................................. 23 Condensers.......... .................................................................................................24 Foam seals............................................................................................................ 25 Condenser electric fans......................................................................................... 25 Evaporators............................................................................................................26 Thermal expansion valve.......................................................................................27 Super heat............................................................................................................. 29 Orifice tube............................................................................................................ 30 Filter drier receiver................................................................................................. 31 Accumulators.........................................................................................................32 “O” rings.................................................................................................................33 Hoses.....................................................................................................................34 Charging ports....................................................................................................... 35 Wiring A/C systems................................................................................................36 Blower speed control............................................................................................. 37 Compressor cycling control....................................................................................38 Protective sensors................................................................................................. 42 Temperature control...............................................................................................48 Mode control.......................................................................................................... 49 Electronic temperature control (ECC).................................................................... 51 (IV) Retrofitting Introduction............................................................................................................ 53 Procedures.............................................................................................................54Automotive Air Conditioning Training Manual 1
  3. 3. (V) Equipment Recovery&Recycling equipment............................................................................56 Evacuation equipment........................................................................................... 57 Charging stations...................................................................................................59 Combination units..................................................................................................60 Refrigerant safety...................................................................................................61 Leak detections & detectors...................................................................................62 (VI) Servicing Lubrications............................................................................................................65 Flushing a contaminated systems..........................................................................66 Preparations...........................................................................................................67 Testing conditions.................................................................................................. 68 A/C performance check......................................................................................... 69 Faulty performance of A/C systems.......................................................................72 A/C system to noisy............................................................................................... 74 A/C system emits unpleasant odours ................................................................... 75 The condenser does not dissipate enough heat....................................................76 Incorrect refrigerant amount...................................................................................77 Compressor displacement regulation valve defective............................................78 Expansion valve defective..................................................................................... 79 Electric compressor clutch slips or does not engage.............................................80 Ice on the evaporator core..................................................................................... 81 Compressor damaged........................................................................................... 82 Hot air infiltrated in the passenger compartment .................................................. 83 Blockage in the A/C system circuit ........................................................................84Automotive Air Conditioning Training Manual 2
  4. 4. TheoryThe four major functionsTo be effective, the automotive air conditioner must control four (4) conditions within thevehicle interior:It must cool the air It must circulate the airIt must purify the air It must dehumidify the airThese functions are essential if passenger comfort is to be maintained when the ambienttemperature and humidity are high.By performing these functions, the air conditioner maintains the body comfort of thepassengers.Automotive Air Conditioning Training Manual 3
  5. 5. TheoryUnderstanding heatWhat is heat?To understand just how an air conditioning system works, we must first understand thenature of heat.For a simple definition we may say that heat is energy. The meshing of gears, the turning ofwheels cause friction which results in heat. Combustion (fire) gives off heat. The burning ofsun radiates heat to the earths surface.Heat in the correct amount will provide life and comfort. Heat in either extreme - extreme tomuch or to little - will be uncomfortable.The control of temperature means the control of comfort.Air conditioning is a method of controlling heat.When is heat hot?When is heat cold?All substances contain heat. Something "feels" hot when it is warmer than our bodytemperature. When something contains less heat than our bodies, we say it feels cold!Cold is merely the removal of some heat.Science tells us that a measurement called "Absolute Zero" is the point at which all heat isremoved from an object (approximately -273 C). Any substance above this absolute zerotemperature retains some heat.The burning of the sun radiates heat to the earth.Automotive Air Conditioning Training Manual 4
  6. 6. TheoryUnderstanding HeatAll substances contain heatThe average person requires a comfortzone of approximately 21 C to 26 C, witha relative humidity of 45 to 50%. In thistemperature and humidity range, we feelmost comfortable. All objects within thissame range are comfortable to touch.As the temperature of anything goesabove or below this range, we think of itas HOT or COLD.Heat measurementA temperature reading gives us the heatintensity of a substance and not theactual quantity of heat.Heat quantity is measured in"KILOCLORIES" (KCALs). One KCAL isthe amount of heat required to raise thetemperature of one kilogram of water onedegree Celsius (at sea level). Thisquantity measurement is used in airconditioning to describe heat transferduring changes of state. 1 00 KCA LWhat causes heat to move? Ambient 25 CHeat always moves from the hotter objects tothe colder one. Whenever there is a transferdifference between two objects, the heatenergy will be transferred from the warmerobject to the cooler one until both objectsstabilize at the same temperature.This is known as the law of heat transfer,and is the basis of air conditioning operation.When a hot cup of coffee is set aside forsome time, it becomes cold. Heat moves outof the hot (90 C) coffee into the cooler (25 C) 90 C 25 Csurrounding air. In time the coffee will reachthe temperature of the surrounding air.Automotive Air Conditioning Training Manual 5
  7. 7. TheoryUnderstanding HeatHow does heat get inside a vehicle?When a car is driven or parked in the sun, heat enters the vehicle from many sources.These sources include:- Ambient air- Sunlight- Engine heat- Road heat- Transmission- Exhaust heatAll of these and other miscellaneous heat sources, increase the air temperature within thevehicle. In a high ambient temperature situation, (e.g. on a 37 C day), the interior of avehicle left standing in the sun with windows closed could reach 65 - 70 C! Sunload Sunload Sunload Engine Heat Exhaust Heat Exhaust Heat Road HeatAutomotive Air Conditioning Training Manual 6
  8. 8. TheoryChanges of stateEvaporationIs the term used when enough heat isadded to a liquid substance to change Vapourit into a vapor (gas). For example,when water is boiled.This condition occurs within the A/Csystem. LiquidCondensationIs the term used to describe theopposite of the evaporation process. If Glassyou take a vapor and remove enough Liquidheat from it, a change of state occurs.The vapor becomes a liquid.The change of vapor to a liquid iscalled condensation. VapourThis condition occurs within the A/Csystem. LiquidFreezingIs another change of state. Freezingresults when heat is removed from aliquid substance until it becomes asolid. Remember that anything above-273 C still contains some heat.In an air conditioning system freezingmust be avoided. Otherwisecomponent damage will occur. LiquidAutomotive Air Conditioning Training Manual 7
  9. 9. TheoryPressure & temperature relationshipTo increase or decrease the boiling point ofa substance, we must alter the pressure onthe substance. Increasing the pressure 70 Cincreases the boiling point.To decrease the boiling point, decrease the Mt Everestpressure. 8848m 100 C Sea levelA good example is the automotive coolingsystem. 110 kPaThe pressure cap keeps the radiator fromboiling over by increasing the pressure onthe coolant.Example:110 kPa radiator cap allows the coolanttemperature to reach 126 C before boiling.This chart opposite shows that the boiling Boiling Point of Waterpoint of water can be altered by changing Pressure Pressure above sea temperature above sea temperaturethe pressure upon it. level C level C (kPa) O O (kPa) C OAs a comparison with the radiator example 0 100 82.7 120.1above. 13.8 103.4 96.5 123.1The substance used in the air conditioning 27.6 106.8 110.3 126.8system, called refrigerant, also boils atdifferent temperatures depending on the 41.4 110.1pressure that it is under. 55.2 113.4 69.0 116.8Automotive Air Conditioning Training Manual 8
  10. 10. TheoryThe ozone layerOzone (O 3 ) is formed in upper atmosphere (stratosphere), approximately 10 to 50 km above theearth surface.This layer acts as a shield that protects the earths surface from harmful ultra violet radiation comingfrom the sun.The chlorine contained in CFCs rise into the ozone layer and destroys the ozone molecule O 3 .Depletion of the ozone layer can be catastrophic to human life causing problems such as:- Skin cancer- Eye cataracts- Reduced immunity to disease- Damage to crops- Reduced aquatic lifeBackground1974 - It was first recognized that the use of chlorofluorocarbons (CFCs) was potentially having adetrimental effect on the ozone layer.1987 - The Montreal protocol was adopted. This protocol called for restrictions on the manufactureand usage of CFCs to 1986 levels. From 1987 manufacturers could only produce the samequantities as produced in 1986.1990 - A second Montreal protocol meeting was held and recommended a total phaseout of ozonedepleting refrigerant by the year 2000.2000 - Total phaseout of CFCs. R LAYE NE OZOAutomotive Air Conditioning Training Manual 9
  11. 11. TheoryR134a PropertiesSince 1993 the Automotive industry of developed countries has started to use anon-ozone-depleting refrigerant HFC 134a (hydrofluorocarbon), its chemical name beingTetra Fluoroethane. We commonly refer to this refrigerant as R134a.R134a was selected as a replacement refrigerant for R12 (Dichlorodifluoromethane)because R12 containing chlorine has a major effect to ozone layer depletion.R134a and water have the same abilities to change the state, but R134a can do this morerapidly and at much lower temperature than water. At anytime above -26.3 C, R134achange its state, becoming a vapor and absorb large quantities of heat from inside thevehicle. This is what creates the cooling effect you feel inside the vehicle.R134a is stored in containers under high pressure. If it is released into the atmosphere, itwill boil at -26.3 C.Automotive Air Conditioning Training Manual 10
  12. 12. TheoryRefrigerant R134aAutomotive Air Conditioning Training Manual 11
  13. 13. TheoryPrinciples of Air Conditioning(Expansion Valve System)High pressure sideLow pressure R134a vapor entering thecompressor is compressed to become highpressure/temperature R134a vapor. This isthen circulated along with lubricant oil to thecondenser. As the high pressure/temperaturevapor travels through the condenser, heat isreleased to the cooler ambient air passingover the condenser tubes condensing thevapor into a liquid. This highpressure/temperature liquid then travelsthrough the filter drier onto the expansionvalve where a small variable orifice provides arestriction against which compressor pushes.Low pressure sideSuction from the compressor pulls the highpressure/temperature liquid R134a throughsmall variable orifice of the TX valve and intothe low-pressure side of the A/C system.The R134a is now under lowpressure/temperature vapor where heat fromthe cabin being blown over the evaporatorcoil surface is absorbed into the colder lowpressure refrigerant The R134a is then pulledthrough the evaporator and into thecompressor. The A/C cycle begins again asthe R134a vapor is compressed anddischarged under pressure.Heat transferR134a in the LOW-PRESSURE side is COLDand can absorb large quantities of heat fromthe air moving over the evaporator.R134a in HIGH-PRESSURE side is HOT andthe cooler ambient air moving over thecondenser can absorb the heat from it.Summary- When the R134a pressure is low, the R134a temperature is low.- When the R134a pressure is high, the R134a temperature is high.Automotive Air Conditioning Training Manual 12
  14. 14. TheoryA/C System with: Thermal Expansion Block Valve, Serpentine Condenser, Serpentine Evaporator(Note: Temperatures shown are examples only)Automotive Air Conditioning Training Manual 13
  15. 15. TheoryA/C System with: Expansion Valve, Parallel Flow Condenser, Plate and Fin Evaporator(Note: Temperatures shown are examples only) o 5C 30oC Plate and Fin Expansion Valve Evaporator o 60 C H/P VAPOUR L/P VAPOUR Compressor H/P LIQUID L/P LIQUID o 70 C Heat given off 60oC Parallel Flow Condenser Filter Drier Receiver o 30 C Ambient temperatureAutomotive Air Conditioning Training Manual 14
  16. 16. TheoryA/C System with: Orifice Tube, Accumulator, Parallel Flow Condenser Plate and Fin Evaporator(Note: Temperatures shown are examples only) o 5C 30oC Plate and Fin Evaporator 60oC Orifice Tube H/P VAPOUR Accumulator L/P VAPOUR H/P LIQUID 70oC Compressor Heat given off L/P LIQUID 60oC Parallel Flow Condenser 30oC Ambient temperatureAutomotive Air Conditioning Training Manual 15
  17. 17. TheoryDual A/C System with: Externally Equalized Expansion Valves (x2), Serpentine Condensers in series (x2), Serpentine Evaporator in parallel (x2), Electrical Refrigerant Flow Shut Off Valves.(Note: Temperatures shown are examples only) Rear Electrical Shut off Valve o Front 0C Electrical Shut off Valve H/P VAPOUR o 70 C L/P VAPOUR H/P LIQUID L/P LIQUID o 60 C 30oC Ambient temperature o 60 C o 30 C Ambient temperatureAutomotive Air Conditioning Training Manual 16
  18. 18. ComponentsCompressorsGeneralThere are various makes and types of compressorsused in automotive air conditioning systems operatingon R134a. The internal design could be Piston, Scroll,Wobble plate, Variable stroke or Vane. Regardless, alloperate as the pump in the A/C system to keep theR134a and lubricating oil circulating, and to increase therefrigerant pressure and thus temperature.Sanden - Wobble plateA reciprocating piston, fixed displacement compressor.The pistons are operated by a wobble plate, whichmoves them backwards and forwards in the cylinders.As the front shaft turns the wobble plate angle changes,causing the pistons to move in and out, pullingrefrigerant vapor in through the suction side,compressing it and discharging this high pressure vaporinto the condenser. Suction/Discharge Connections Connecting Wobble Piston Rod Plate Low Pressure Vapour @M ¢ Q À € Charge Ports Intake/Discharge Valves Cylinder High Pressure Cam Clutch Head Vapour Rotor AssemblyAutomotive Air Conditioning Training Manual 17
  19. 19. ComponentsCompressorsScroll type - SandenThis compressor uses a unique design with two scrolls,one fixed and one is movable, both are inter-leaved.The movable spiral is able to ORBIT or oscillate withoutactually fully rotating. The movable scroll is connectedto the input shaft via a concentric bearing. As themovable spiral oscillates within the fixed spiral, anumber of pockets are formed between the spiral. Asthese pockets decrease in size the refrigerant issqueezed, the pressure increases and is dischargedthrough a reed valve at the discharge port in the rearsection of the compressor. Suction Pressure Area Field Coil Clutch Front Pressure Plate Discharge Valve Clutch Rotor Pulley Discharge Pressure Fixed Area Movable Scroll ScrollCompression CycleAutomotive Air Conditioning Training Manual 18
  20. 20. ComponentsCompressorsVariable stroke - Harrison V5The Delphi (Harrison) V5 compressor is a non-cycling variable displacement compressor.The compressor varies displacement to control capacity to meet A/C system demand at alloperating conditions. The compressor features a variable angle wobble plate in five (V5)cylinder axial piston design.Displacement is controlled by a bellows actuated control valve located in the rear cylinderhead. This control valve senses and responds to the system suction pressure or A/C systemdemand. Through regulation of compressor crankcase pressure, the wobble plate angle, andtherefore compressor displacement is variable.In general, the compressor discharge pressure is much greater than the compressorcrankcase. Which is greater than or equal to the compressor suction pressure. At maximumdisplacement, compressor crankcase pressure is equal to the compressor suctionpressure. At reduced or minimum displacement, the compressor crankcase pressure isgreater than the suction pressure. A/C Demand Low Reduced or Minimum Displacement A/C Demand Wobble Plate High (Reduced or Pivot Maximum Minimum Angle) Displacement Control Valve Wobble Plate (Maximum Angle)Automotive Air Conditioning Training Manual 19
  21. 21. ComponentsCompressorsRotary Vane - PanasonicRotary vane compressors consist of a rotor with three or four vanes and a carefully shapedrotor housing. As the compressor shaft rotates, the vanes and housing form chambers.The R134a is drawn through the suction port into these chambers, which become smaller asthe rotor turns. The discharge port is located at the point where the gas is fully compressed.The vanes are sealed against the rotor housing by centrifugal force and lubricating oil. Theoil sump and oil pump are located on the discharge side, so that the high pressure forces oilthrough the oil pump and then onto the base of the vanes keeping them sealed against therotor housing.During idle an occasional vane noise from the compressor may be heard. This is due to thetime taken for lubricating oil to circulate through the A/C system. Discharge Port Discharge Valve Clutch Assembly Oil Pump Vane Oil Reservoir Rotor BodyAutomotive Air Conditioning Training Manual 20
  22. 22. ComponentsCompressors and Mount & DriveMount & DriveConsists of a bracket to mount the compressor to the engine, a belt idler pulley, compressordrive belt and possibly and extra drive pulley for the crankshaft.Compressor MountManufactured of either plate, cast iron, steel or aluminium, this bracket should exhibitexcellent noise absorption qualities especially if using a piston type compressor.Idler PulleyA small pulley normally used in conjunction with a belt adjusting mechanism, also used whena belt has a long distance between pulleys to absorb belt vibrations.Drive PulleySome vehicles do not have an extra pulley to accommodate an A/C drive belt, in thesecases an extra pulley is bolted onto the existing crankshaft pulley.Multiple Belt Drive Serpentine Belt Drive Idler Pulley Poly “V” Power Groove Power Steering Steering “V” Groove Pump Pump Idler Pulley Alternator Alternator Compressor Compressor Water Pump Water Pump Pulley Pulley Air Pump Crankshaft Air Pump Crankshaft Pulley PulleyAutomotive Air Conditioning Training Manual 21
  23. 23. ComponentsClutchesCompressor ClutchThe clutch is designed to connect the rotor pulleyto the compressor input shaft when the field coilis energized. The clutch is used to transmit thepower from the engine crankshaft to thecompressor by means of a drive belt.When the clutch is not engaged the compressorshaft does not rotate and refrigerant does notcirculate the rotor pulley free wheels. The fieldcoil is actually an electromagnet, once energizedit draws the pressure plate towards it, locking therotor pulley and the pressure plate togethercausing the compressor internals to turn, creatingpressure and circulating refrigerant. Pulley Front Plate Retaining Pulley Bearing Circlip Adjusting Shim Pulley Field Coil (Front Plate Air Gap)Automotive Air Conditioning Training Manual 22
  24. 24. ComponentsLubricationR134a is part of the air conditioners lubrication system. NEVER operate an A/C systemwithout refrigerant as there will be no lubrication for the compressor and internal damage willoccur.Refrigerant oil is circulated around the A/C system saturated in the refrigerant.Ariazone recomends PAOil as best automotive compressor lubricant.PAOil is a Polyalpha Olefin, Not a PAG or an Ester. This is a fully synthetic oil,carefully blended to be a superior oil. It is so good that it can be used in allautomotive compressors, whatever the brand. Its a non-agressive, safe oilthat wont effect seals or hoses and is compatible with other lubricants.And its non-hygroscopic. www.rocoil.com PAOil PAG oil POLYOLESTER oil MINERAL oil NON Hygroscopic Hygroscopic Hygroscopic Hygroscopic COMPATIBLE NON COMPATIBLE NON COMPATIBLE NON COMPATIBLE with other lubricants with other lubricants with other lubricants with other lubricants COMPATIBLE with: HCFCs NOT COMPATIBLE COMPATIBLE COMPATIBLE CFCs NOT COMPATIBLE COMPATIBLE COMPATIBLE HFCs COMPATIBLE COMPATIBLE NOT COMPATIBLE HFC BLENDS COMPATIBLE COMPATIBLE NOT COMPATIBLE HCFC BLENDS NOT COMPATIBLE COMPATIBLE NOT COMPATIBLE LOW MISCIBILITY MISCIBILE MISCIBILE MISCIBILE PREVENTS OIL LOGGING MAY NOT PREVENT OIL LOGGING MAY NOT PREVENT OIL LOGGING MAY NOT PREVENT OIL LOGGING INCREASES CAPACITIES GIVING SHORTER RUN UNLIKELY TO UNLIKELY TO UNLIKELY TO TIMES FOR THE SAME INCREASE CAPACITIES INCREASE CAPACITIES INCREASE CAPACITIES LOADSUPERIOR HIGH FAIR HIGH FAIR HIGH POOR HIGHTEMPERATURE VISCOSITY TEMPERATURE VISCOSITY TEMPERATURE VISCOSITY TEMPERATURE VISCOSITYPROPERTIES PROPERTIES PROPERTIES PROPERTIES NON AGGRESIVE AGGRESIVE AGGRESIVE NON AGGRESIVE A TOTALY SAFE PRODUCTPrecautions when using PAG oil:- Do not allow PAG oil to contact bare skin or vehicle paintwork.- Flush skin immediately when using PAG oil.- Avoid breathing PAG oil/R135a mixture.- PAG oil is highly hygroscopic. Open containers only when ready to use. Cap container immediately after use.Automotive Air Conditioning Training Manual 23
  25. 25. ComponentsCondensersThe Condenser function is to act as a heat exchanger and allow heat to flow from the hotrefrigerant to the cooler outside air.R134a entering the condenser will be a high-pressure high temperature vapor. As the R134avapor travels through the tubes of the condenser heat is given off to the cooler ambient air; therefrigerant vapor condenses and changes to a liquid state.At this point a large amount of heat is given off by the R134a. The refrigerant will now be a hot,high pressure liquid.Design typesSerpentineThis type of condenser consists of one long tube which is coiled over and back on itself withcooling fins in between the tubes.Parallel flow design(Recommended for R134a)This design is very similar to a cross flow radiator. Instead of refrigerant travelling through onepassage (like serpentine type), it can now travel across numerous passages. This will givelarger surface area for the cooler ambient air to contact. Serpetintine Flow Parallel Flow IN High Pressure IN High Pressure Baffles Vapour From Vapour From Compressor Compressor OUT High Pressure OUT High Pressure Liquid to filter Drier Heat given off from Liquid to filter Drier Refrigerant to cooler surrounding airR134a - R12 Comparison- As R134a operates on higher pressures, less internal flow, restrictive and improved heat rejection condensers are required.- Most manufacturers select the parallel flow design for this version. They are approximately 25% more efficient than the serpentine condensers.Automotive Air Conditioning Training Manual 24
  26. 26. ComponentsFoam SealsFoam seals Without Foam SealsThese seals are fitted in between thecondenser and radiator to prevent theheated ambient air exiting above, below orto the sides of the space in between(normally 25mm) the radiator andcondenser.As ambient air is drawn through condenserby the condenser or radiator fan, itstemperature increases. If gaps are presentbetween the condenser and radiator thisheated air can be circulated back throughthe condenser. This results in the increasedcondenser temperature and causesreduction in the performances of the A/C Fan Typessystem.Condenser electric fanMost vehicles with air conditioning requirean electric fan to assist air flow, eitherpushing or pulling the air through the Conventional Skewcondenser, depending on which side of the (By reversing the fancondenser the fan is placed. blades it can either push or pul the air)The majority of vehicles using R134arequire this additional condenser coolingdue to the higher operating pressures ofR134a. Also most modern vehicles now Basic Circuithave smaller grilles or bumper baropenings. This causes poor air flow Comppresorconditions especially by the amount of airflow over the condenser. 30Amp RelayThe condenser fan is operated with A/Cengaged in various ways: Power to Compressor- Medium pressure switch;- Indirect connection to the compressor clutch- Via the Electronic Control Module (ECM); Fuse 25 Amp- Signal from the A/C switch activation.R134a - R12 ComparisonIncreased use (operation time) with R134a systems due to higher refrigerant temperature.Automotive Air Conditioning Training Manual 25
  27. 27. ComponentsFoam SealsR134a enters the evaporator coil as a cold Serpentine evaporatorlow-pressure liquid. As this liquid passesthrough the evaporator coil, heat moves from Same design as the serpentinethe warm air blowing across the evaporator condenser but approximately five timesfins into cooler refrigerant. This air that has deeper.now been cooled is then ducted into thecabin via the blower motor. Serpentine evaporatorWhen there is enough heat to cause a INLETchange of state, a large amount of the heat Low Pressure Liquidmoves from the air to the refrigerant. Thiscauses the refrigerant to change from a low-pressure cold liquid into a cold vapor. (Latentheat of evaporation).As the warmer air blows across theevaporator fins, moisture contained in that air(humidity) will condense on the coolerevaporator fins. Condensed moisture then OUTLETruns off through the drain tubes located at the Low Pressure Vapourunderside of the evaporator case.Plate & Fin Laminated EvaporatorsSimilar operation to the parallel flow condenser were the refrigerant has a multi flow passcreating a large surface area.Plate & Fin Laminated Evaporator ( Recommended for R134a) Separating INLET Baffles Low Pressure Liquid OUTLET Low Pressure Vapour to compressorR134a - R12 ComparisonMost manufacturers prefer to use the plate and fin design for R134a because of 20%performance increase over the serpentine design.Automotive Air Conditioning Training Manual 26
  28. 28. ComponentsThermal Expansion ValvesRefrigerant flow to the evaporator must be TXV - Closedcontrolled to obtain maximum cooling,while ensuring that complete evaporation 8.of the liquid refrigerant takes place. This isaccomplished by the thermal expansion 7.valve (TXV). 3. (F1)Pressures in controlAs shown in the illustration, the TXVcontrols the refrigerant flow by using a 2.system of opposing pressures which willcall: AF1 - Temperature sensing capillary tube 5.Sealed tube filled with refrigerant. This 4.refrigerant is also filled above thediaphragm (7). The capillary tube sensingbulb (3) is attached to the evaporator 6. (F3)outlet tube surface.F2 - Pressure compensation tube 9. 1. (F2)This is a hollow tube connected to theevaporator outlet tube and senses the High Pressure liquidpressure of the R134a refrigerant leavingthe evaporator coil. (Other TX valves may 1. From Filter Drier 6. Springnot use this tube as pressure is provided 2. To Evaporator Inlet 7. Diaphragminternally within the valve). 3. Capillary tube 8. Refrigerant 4. Metering Orifice 9. Pressure CompensatingF3 - Pressure spring 5. Ball valve TubeThis spring (6) is located under the ballvalve (5). TXV - OpenOperation 8.Open 7. 3.When the evaporator outlet tube (F1)temperature increases, the refrigerant (3)in the capillary tube expands, forcing thediaphragm (7) downwards and thus 2.pushing pin (A) also downwards causingthe ball valve (5) to move away from themetering orifice (4), allowing more R134a A Lowto enter the evaporator inlet side. Pressure 5. liquid 4.ClosedAs the evaporator outlet tube becomescooler, the refrigerant in the capillary tube(3) contracts. Forces F2 and F3 cause thediaphragm (7) and pin (A) to move upward 6.allowing the ball valve to move towards the (F3) 9.metering orifice (4), restricting the R134a 1. (F2)flow. The outlet tube gets warmer and the High Pressure liquidprocess starts over.Automotive Air Conditioning Training Manual 27
  29. 29. ComponentsThermal Expansion Block Valve TXV - OpenThe block valve differs from the previously 9. 11.mentioned expansion valve in that it has four F1passages, although the basic operation isexactly the same. Operation of the block 10. 12.valve is still via refrigerant F2expansion/contraction within a diaphragm 3. 4.(11), but not sensed through separate tube(capillary tube). It is sensed by changes inthe refrigerant temperature and pressure Lowpassing from the evaporator outlet through Pressurethe block valve. 2. Liquid 1.As the refrigerant from the outlet side of theevaporator passes over the sensing element(12), expansion or contraction of the Highrefrigerant takes place causing the activating 5. Pressurepin (8) to move the ball valve (6) away or Liquid 6.closer to the metering orifice. This allows 8.more or less refrigerant to enter the 7. F3evaporator coil inlet.Pressures in control 1. From Filter Drier 8. Activating PinAs shown in the illustration, the block valve 2. To Evaporator Inlet 9. Refrigerantcontrols refrigerant flow by using a system of 3. From Evaporator 10. Pressure Compensationopposing pressures which we will call: 4. To Compressor under Diaphragm 5. Metering Orifice 11. Metallic Diaphragm 6. Ball 12. Sensing ElementF1 - Temperature sensing 7. SpringThis is a sealed diaphragm and sensorcontaining refrigerant. As refrigerant leavingthe evaporator coil outlet passes over TXV - Closedsensing element (12) the refrigerant (9) 11. 9.above the diaphragm (11) expands moving F1pin (8) downwards pushing ball valve (6)away from the metering orifice (5). 10. 12. F2F2 - Pressure compensationThis is a passage (10) in the block valve 3. 4.outlet side where refrigerant can build upunder the diaphragm (11) to act as anopposing pressure to help regulate theamount of refrigerant into the evaporator coilinlet side. 1. 2.F3 - Pressure springThis spring (7) is located under the ball valve(6) and acts as an opposing force trying to 5. High Pressuremove the ball valve towards the metering 6. Liquidorifice (12) and to reduce refrigerant flow to 7. 8.the evaporator coil inlet. F3Automotive Air Conditioning Training Manual 28
  30. 30. ComponentsSuper HeatAt a certain point in the evaporator the R134a refrigerant is completely vaporized, after thatpoint any additional heat absorbed by the R134a vapor is described as SUPER HEAT.The value of this SUPER HEAT is the temperature difference above the point at whichR134a liquid changes to a vapor.The thermal expansion valve (TXV) values are preset at factory to compensate for the superheat. Ensure when a TX valve is replaced it is of the type suited to the A/C system.Saturation temperature = The temperature at which refrigerant in liquid form changes to avapor at a given pressure.Actual temperature = The temperature of refrigerant at the evaporator outlet.Example - Calculation for super heatActual temperature - 10 C minusSaturated temperature - 5 CSuper heat = 5C 247 Kpa 5oC Saturated Temperature From Filter Dryer 10oC To Compressor Actual Temperature 10oC 247 KpaAutomotive Air Conditioning Training Manual 29
  31. 31. ComponentsOrifice TubeAt the orifice tube the R134a is forced to flowthrough a fine restriction (orifice). This causesa pressure drop and temperature drop in theR134a entering the evaporator.The rate of flow depends on the pressuredifference across the restriction.A fine gauze filter is located at the inlet andoutlet sides of the orifice tube to filter anycontaminates from passing onto theevaporator.Orifice tubes have different size restrictionsdepending on the A/C system; these differentsizes can be identified by the outer plastictube color. To Evaporator Fine Mesh Fine Mesh Filter Outlet Filter Inlet “O” Rings Low Pressure Liquid Fixed Small Diametar Bronze Tube High Pressure Liquid From (Restriction) CondenserAutomotive Air Conditioning Training Manual 30
  32. 32. ComponentsFilter Drier ReceiverThe filter drier acts as a particlefilter, refrigerant storagecontainer and most importantlymoisture absorber. From Condenser To Evaporator High HighMoisture, temperature and Pressure PressureR134a causes hydrofluoric and Liquid Liquidhydrochloric acid. The silica gelbeads (desiccant) located in theFDR absorb small quantities ofmoisture thus preventing acidestablishment. StrainerMost R134a filter dryers haveNO sight glass. This is becauseat approximately 700Crefrigerant temperature the PAGoil will foam giving a falseimpression of low gas charge. Ifthe FDR does utilize a sightglass ensure correct diagnosiswhen viewing.Note: Ensure the connectionindicated with the word "IN"is connected to thecondenser outlet. N NImportant: Never use an R12FDR on a R134a system. Desicant Strainer High Pressure LiquidAutomotive Air Conditioning Training Manual 31
  33. 33. ComponentsAccumulator (Orifice Tube System)The function of the accumulator is to store refrigerant, filter particles, absorb moisture andseparate vaporous R134a from liquid R134a.The normal process of the Orifice Tube system works when R134a leaves the evaporatorcoil as a mixture of vapor and liquid. This liquid enters the accumulator and falls to thebottom. The vapor rises to the top and continues onto compressor. The liquid R134a in thebottom of the accumulator gradually vaporizes off. This vapor rises, then pulls into thecompressor. Vapour Pick Up Tube From To Evaporator Compressor Low Pressure Low Pressure Liquid/Vapour Vapour Desiccant LiquidAutomotive Air Conditioning Training Manual 32
  34. 34. Components“O” RingsThe "O" ring rubber compound used for R134aA/C system joints, fittings and components is ahydrogenated nitrile butadiene rubber (HNBR)and identified by the color green."O" ring lubrication can be carried out usingmineral oil. All hoses tubes and componentsincluded in an A/C kit are pre-lubricated, as arethe "O" rings supplied as a spare part. Othermanufacturers could use "O" rings of a differentcolor and size. Ensure that only the approved"O" ring is used for the type of system beingserviced or repaired. R12 R134aR134a - R12 Comparison- R12 “O” rings coloured black- NEVER use R12 “O” rings with R134a as the “O” ring will be damaged owing to the lack of chlorine in R134a- You can use R134a “O” rings in an R12 systemAutomotive Air Conditioning Training Manual 33
  35. 35. ComponentsHosesOWING TO THE SMALLER MOLECULARSIZE AND HIGHER OPERATINGPRESSURES OF R134a, the refrigerant hosenow incorporates a nylon inner lining. This isto reduce the normal refrigerant leakage thatwould naturally occur through the porosity ofrubber hoses.Most R134a hoses have a smaller outsidediameter and thinner hose walls to improveflexibility and reduce noise levels within theA/C system.R12 R134a Rubber Reinforcement Rubber Nitrile Rubber Reinforcement Rubber Nylon NitrileR134a - R12 Comparison- NEVER use new R12 hose (unless of a barrier type) in an R134a A/C system. The PAG oil and hydrogen contained in the R134a causes the normal R12 nitrile hoses to rapidly deteriorate.- R12 hoses have normally large outside diameters. This could create higher noise levels,Automotive Air Conditioning Training Manual 34
  36. 36. ComponentsCharging PortsCharging ports are fitted onto components such as hoses, tubes and filter dryers receivers.These charge ports enable the A/C system to be serviced and tested whilst under pressure.Different size ports identify the high and low sides of the A/C system. A plastic cap withrubber seal is used to close the charge port opening and avoid leaking.A dedicated design of charging valve has also been developed to suit the R134a chargingports.Most schrader valves will leak slightly. Ensure that the plastic protection cap is fitted.Schrader valves designed for R134a must only be used in R134a systems. This is becauseof the seal material used.R134a Quick Coupler R134a Charging Port Open Close Hand Wheel Shrader (Open/Close Valve Shrader Valve) Rubber Sealing Washer Top of Cap Charging Port Charging PortR12 Charging Port Protective Cap Shrader Valve 1/4” or 3/16” Charging PortAutomotive Air Conditioning Training Manual 35
  37. 37. ComponentsWiring A/C SystemControl/Wiring layout(Series Connection)Pressure switches are connected in series with the compressor clutch. If an "under" or"over" system pressure occurs the pressure switch will "open circuit" breaking the circuit tothe compressor clutch.With electronic fuel injected vehicles the ELECTRONIC CONTROL MODULE (ECM) isusually interconnected into the A/C wiring circuit. When the A/C switch is engaged a requestsignal is sent to the ECM, if the A/C circuit is intact, i.e. the pressure switches are a closedcircuit, the ECM activates a relay by creating an earth and power is supplied to thecompressor clutch. Also an RPM increase generally takes place to avoid engine stall whilstat idle. Power Fuse Low A/C Pressure Switch Switch B8 Blower Thermostatic High Switch Switch Pressure Switch ECM Thrmal A/C Protector Relay C2 Diode Compressor A/C Relay Clutch Field Energised only if Coil the ECM provides the EarthAutomotive Air Conditioning Training Manual 36
  38. 38. ComponentsBlower Speed ControlsCoil type Coil TypeThis blower speed regulator simplyconsists of coiled wires connected inseries. These coiled wires are of variedthickness. The current flows througheither one or a combination of all thecoils. The resistance of the coil(s) alterthe blower speeds.The highest blower speed when selected Fan Speedis normally from direct battery voltage via Resistancea relay. CoilsElectronic Electronic TypeThe function of the electronic controller is Electronicto convert low current signals from the ModiualECM to a higher current, varying thevoltage to the blower motor. Blowerspeeds may be infinity variable andusually can use up to 13 speeds.This type of speed controller is normallyused with the electronic climate control(ECC) system. The highest blower speed Heatwhen selected is normally from direct Sinkbattery voltage via a relay.Electronic Type Coil Type IGN 12V 2. 3. Blower Switch or Control Speed 1 +12V Blower Motor To Blower Relay Blower Speed 4.Automotive Air Conditioning Training Manual 37
  39. 39. ComponentsCompressor Cycling ControlsThermostatic switch (Anti ice-up device)The thermostat is connected in series to thecompressor clutch. When the temperatureof the evaporator coil approaches freezing Switch(00C), this temperature is sensed by the Pointthermostat capillary tube which is in contactwith the evaporator fins. The capillary tube Bellowscontains refrigerant which expands or Filled withcontracts depending on the temperature on Refrigerantthis tube. The points inside the thermostaticswitch open up when the refrigerant in thecapillary tube contracts (sensing a cold Capillaryevaporator coil) and interrupt the A/C Tubeelectrical circuit turning the compressor off.When the evaporator temperature risesagain to a preset point (4 - 5 0C) thethermostat points then close. Therefrigerant in the capillary tube hasexpanded (sensing a warmer evaporatorcoil and the electrical circuit is re-established to the compressor clutch.Electrical Circuit Clutch Coil Ground Ignition Resistor Blower Motor Thermostat Switch Combination A/C and Blower SwitchAutomotive Air Conditioning Training Manual 38
  40. 40. ComponentsCompressor Cycling ControlsThermistor & AmplifierThis has the same function as thethermostatic switch except rather thenmechanical action with contact points and Amlifiercapillary tube, the thermistor and amplifier iselectronically activated. The thermistor is asensing probe but unlike the thermostatcapillary tube it senses the air temperaturecoming off the evaporator coil.ThermistorElectrical wiring containing a sensor whichis a NTC resistor.(Negative Temperature Co-efficient). ThermistorAmplifierA small electronic device containing a circuitboard and electrical components.Thermistor resistance is amplified and usedto control or switch the A/C clutch on or off.Economy modeThis function is normally associated with theuse of a thermistor amplifier. In economy(ECON) mode the compressor cut outtemperature is set higher than a normal A/Cmode. This means the compressor stays onfor a lesser time, decreasing engine loadand improving fuel economy and engineperformance.Center vent temperatures will also be A/C ECONslightly higher due to the compressor Switchescycling off at a higher evaporatortemperature.Automotive Air Conditioning Training Manual 39
  41. 41. ComponentsCompressor Cycling ControlsPressure cycling switch - ElectricalSome vehicles using the Cycling Clutch Orifice Tube (CCOT) system utilize a pressureswitch located in the low side of the A/C system between the evaporator and compressorfor compressor control.This pressure switch is electrically connected in series with the compressor clutch.Once the low side pressure reaches approximately 200 kPa, the compressor clutch isdeactivated by the pressure switch opening. A low side pressure of approximately 200 kPacorresponds to an evaporator coil temperature of approximately + 0.40C (above freezingpoint).Once the compressor is deactivated the low pressure rises followed by the evaporator coiltemperature rising. At a pre-determined low pressure point, the pressure switch reactivatesthe compressor clutch. The evaporator temperature lowers again and the compressorre-engages.Note: Normally a low pressure cut off switch is not used with a pressure cycling switch asthe pressure cycling switch is located on the low side. It serves as a low pressure cut offalso. High Pressure Switch Pressure Cycling Switch Compressor Clutch Disengages at approx. 200 kPa Re-engages approx. 350 kPaAutomotive Air Conditioning Training Manual 40
  42. 42. ComponentsCompressor Cycling ControlsPressure Control Valve - MechanicalA/C Demand HighDuring periods of moderate to high A/C demand, system suction pressure will be greaterthan the control valve set point. During these periods, the control valve maintains a bleedfrom crankcase to suction. Crankcase pressure is therefore equal to suction pressure. Thewobble plate angle, and therefore compressor displacement is at its maximum.A/C demand lowDuring periods of low to moderate A/C demand, system suction pressure will decrease tothe control valve set point. The control valve maintains a bleed from discharge to crankcaseand prevents a bleed from crankcase to suction. The wobble plate angle, and thereforecompressor displacement is reduced or minimized. During these periods, displacement isinfinitely variable between approximately 5 and 100% of its maximum displacement.Harrison Variable Stroke Compressor Discharge From Discharge Crankcase Chamber Valve To Compressor Crankcase Suction Crankcase From Compressor Valve Crankcase Crankcase To Suction Control Chamber Valve Discharge Pressure Suctione Pressure Crankcase PressureAutomotive Air Conditioning Training Manual 41
  43. 43. ComponentsProtection DevicesClutch DiodeThe clutch coil is an electromagnet with a strong magnetic field when current is applied.This magnet field is constant as long as the clutch is applied. When the power is removedthe magnetic field collapses and creates high voltage spikes. These spikes are harmful tothe ECM and must be prevented. A diode placed across the clutch coil provides a path toground. This diode is usually taped inside the clutch coil connector. Diode Compressor Thermal Clutch Protection SwitchThermal protection switchThe thermal protection switch is normallylocated on the compressor housing. Thisprotection switch is used to preventcompressor damage through internal friction.This switch senses the compressor casetemperature and once this case temperaturereaches a predetermined figure the electricalcircuit to the compressor clutch is interrupted.As the thermal protection switch is connectedin series with the compressor clutch once the Fixedcompressor case temperature lowers to a Contactpredetermined figure the compressor clutch is Bimetalicthen re-energized. striplAutomotive Air Conditioning Training Manual 42
  44. 44. ComponentsProtection DevicesRefrigerant Pressure SwitchesLow pressure Refrigerant PressureUsed to interrupt the electrical circuit to the Diapraghmcompressor clutch. If the refrigerantpressure is too low or a problem exists inthe A/C refrigerant system. (refer diagram).High pressureThe power supply is interrupted when the Activating Contactsrefrigerant pressure is too high or a Pinproblem exists in the A/C refrigerantsystem. Power Compressor ClutchTerminologyBinary switch - High/Low switch.Trinary switch - High/Medium/Low switch.Condenser fan control 1770kPaMedium pressure (example)Used to engage the condenser fan at a pre-determined refrigerant pressure.Example: Condenser fan high speedactivation at 1770kPa refrigerant pressure.These switches can be individual or acombination of the two or even threepressure ranges.Automotive Air Conditioning Training Manual 43
  45. 45. ComponentsProtection DevicesPressure TransducerThe pressure transducer is a sealed gauge reference, capacitive pressure sensor with onboard signal conditioning. It provides a 0.5 volt output and requires a 5 volt regulated powersupply.In operation the transducer sensor applies pressure via the deflection of a two piececeramic diaphragm with one half being a parallel plate capacitor. Changes in capacitanceinfluenced by the refrigerant pressure under the ceramic diaphragm are converted to ananalog output by the transducer integral signal electronics.The pressure transducers electronics are on a flexible circuit board contained in the uppersection of the transducer and provide linear calibration of the capacitance signal from theceramic sensing diaphragm.Benefits of using the pressure transducer over a normal type pressure switch is that thetransducer is constantly monitoring the pressures and sending signals to the electroniccontrol module (ECM), unlike the normal type pressure switch that has an upper and lowercut out points. The ECM will disengage the A/C compressor at low or high refrigerantpressures and electronic diagnostic equipment can be used to extract system pressureinformation making it easier when diagnosing problems. High Side Charge port Signal Electronic Ceramic Diaphragm Pressure Pressure port TransducerAutomotive Air Conditioning Training Manual 44
  46. 46. ComponentsProtection DevicesEngine Control Module (ECM)Body Control Module (BCM)Power Train Module (PCM)Microprocessors (ECM, BCM & PCM) are used to engage and disengage the A/C electricalcircuits controlling the compressor and condenser fan.Numeric signals from various sensors relating to engine speed, road speed, coolanttemperature, A/C switch activation, pressure switches, A/C thermostatic switch, throttleposition and kickdown are constantly monitored by the ECM, BCM or PCM. These numericsignals are converted in the microprocessors to calculations required to:- Deactivate the A/C compressor at high/low system pressures;- Deactivate the A/C compressor at kickdown;- Active and deactivate the condenser fan;- Increase engine idle speed when A/C system is activated;- Deactivate the A/C compressor at high engine RPM;- Delay A/C compressor engagement at engine cranking;- Activate electrical engine fan at predetermined coolant temperature;- Deactivate the A/C compressor when coolant temperature excessive;- Deactivate the A/C compressor at wide open throttle (WOT) Fuse PCM High Thermostatic Pressure Switch Switch B8 Blower A/C Low Fuse Switch Pressure Switch Compressor A/C Clutch Field Relay Coil C2 Diode A/C Relay Energised only if the ECM Thermal provides the Protector Earth Engine Cooling A/C Pressure Fan Relay High Switch Speed Fuse F6 Fan Fusible Two Speed Engine Cooling Fan Engine Cooling Link Fan Relay High Speed Control BCM Engine Cooling Fan Relay Low Engine Cooling Fan Speed Control Relay Low SpeedAutomotive Air Conditioning Training Manual 45
  47. 47. ComponentsProtection DevicesRelaysRelays are normally used in the A/C electricalcircuit to protect switches that have a low currentcarrying capacity (i.e. a small contact area/weakpressure contact point) or for current drawdifferences between components.Shown below is an example of the difference in acircuit with and without a relay.Without Relay A/C Switch 10V Battery Compressor 12V ClutchWith Relay A/C Switch A/C Switch Energises Battery Relay 12V Compressor Clutch 12VAutomotive Air Conditioning Training Manual 46
  48. 48. ComponentsSensorsSunloadThe sunload sensor is a photochemical Sunload Sensordiode (PCD) located on top of thedashboard. This sensor sends a signal tothe electrical climate control module (ECCM)indicating the strength of the sunlight(sunload) which influences the vehicleinterior temperature.If the sunload is high as signaled by thesunload sensor the ECCM will activate thehighest blower fan speed and maximumcooling to compensate for this additionalradiated heat load. Likewise, if the sunloadis low (cloud cover) as sensed by thesunload sensor, the ECCM will reduce theblower fan speed and the system will notoperate at maximum cooling.Ambient temperature sensorThe ambient temperature sensor is anegative coefficient resistor (NTC) with lowvoltage input. The sensor alters resistancedepending on the ambient air temperaturesurrounding it.The sensor is located in the ambient airstream normally behind the bumper bar orfront grille area. This sensor is used tomonitor the outside temperature and isinterconnected to a visual display in theinstrument panel. Ambient Temperature SensorAutomotive Air Conditioning Training Manual 47
  49. 49. ComponentsTemperature ControlAir Mix DoorTemperature control is carried out by operating the temperature mode control, normallycable operated and connected to a door housed in the heater case. This door is locatedabove the heater core and in the full cold position, completely covers the heater core. Asmore heat is required the door is operated and moves away from the heater core and allowsradiant heat to rise and mix with the fresh or A/C air to increase the vent temperatures to thedesired comfort level required.Air Flow during Maximum Hot Air Flow during Maximum Cold Air Mix Air Mix Door Door Heater Heater Core CoreHeater Control Plunger Actuating Level connected to theThe heater tap is normally vacuum Temperatureoperated and has engine vacuum applied Control via a Rodto it in the full cold position. This stopsthe flow of coolant to the heater core bykeeping the heater tap closed.Once heating has been selected, thevacuum is exhausted from the vacuumcircuit via a vacuum switch, to the heatertap and the hot coolant then flows Vacuum From Switch Vacuumthrough to the heater core. Source To Mode ControlAutomotive Air Conditioning Training Manual 48
  50. 50. ComponentsMode ControlVacuum Actuators Single Stage-Single & Dual stageThe various air distribution duct doors Þlocated in the heater-A/C case are open andclosed using a vacuum actuator. ÞThe vacuum actuator consists of a plastic ormetal container housing, a spring, rubberdiaphragm and a connecting rod. Once Vacuumvacuum is applied, the rubber diaphragm is Released Þpulled back bringing with it the connectingrod which is connected via a lever to an airdistribution door and compressing thespring. When the vacuum is removed, thespring pushes the diaphragm and Vacuum Appliedconnecting rod back to original position.Duel Stage Vacuum port Spring 1nd Stage 1nd Stage Diaphragm 2nd Stage Housing 1nd Stage (Half) Vacuum port Fully Extended 2nd Stage Actuation Rod Spring 2nd Stage DiaphragmVacuum circuitVacuum is directed to the desireddistribution duct vacuum actuator, fromengine intake manifold vacuum. Mode DirectionA vacuum switch attached to the mode Control Modecontrol knob redirects vacuum to the Vacuum Controldesired vacuum actuator. Vacuum ActuatorsAutomotive Air Conditioning Training Manual 49
  51. 51. ComponentsMode ControlAir mix motorsThe air mix motor is actually a potentiometerbalance resistor (PBR). It comprises of smallelectrical motor, gears of varying sizes, a driveshaft and a printed circuit board. It is attachedby means of a drive shaft to the air mix ortemperature mode door main shaft. This motorregulates the temperature by moving the doorcloser to (cooler) or further from (hooter) theheater core.Variable low voltage signals are sent from theelectronic climate control module (ECC) tomove the air mix motor - which in turn movesthe temperature mode door, to a predeterminedposition to regulate the vehicle interiortemperature. The air mix motor position signalsare also sent back to the ECC for reference asto where the air mix/mode door is positioned.Vacuum solenoid pack ActuatorThis method for operating the vacuum actuatorsis normally used in conjunction with theelectronic climate control system (ECC). Thistype of climatic control is fully electronic. Thevacuum actuators used for various airdistribution modes are indirectly engaged anddisengaged electronically via the vacuumsolenoid pack.The solenoid pack consists of a group ofelectrically activated vacuum solenoid valvesusing a common printed circuit board whileenclosed in a single housing.Each solenoid is allotted to a vacuum actuatoror vacuum valve (heater valve). Once thevacuum solenoid is energized by the ECC, an Vacuum Solenoidengine supplied vacuum can then flow through Packthe solenoid valve to the relevant vacuumactuator to operate a mode. Likewise, once thevacuum solenoid is de-energized it then ventsthe vacuum from the line and actuator into theatmosphere.Automotive Air Conditioning Training Manual 50
  52. 52. ComponentsElectronic Temperature Control (ECC)ECC systems operate with the same basic component as in the manually controlledsystems, such as the condenser, compressor, evaporator and heater. The major differencebeing that the ECC system can maintain a preset level of cooling or heating selected by thevehicle operator once the automatic mode is selected.Electronic sensoring devices allow the ECC to respond to various changes in sunload,interior cabin temperature and ambient temperature. The ECC system will adjustautomatically to any temperature and climatic changes to keep the vehicle cabin interiorwithin the pre-selected temperature range.This is accomplished by adjusting:- Blower fan speed- Air mode positions- A/C activation- Heater tap activation- Air mix door movement- Fresh/Recirc door position Control In Car Temperature Display Air Mix Sensor Door Motor AMB Sunload -88.8C AMUATNOU A L A/C Vacuum Sensor Solenoid Pack A 123 CLIMATE CONTROL 0FF AUTO MANUAL MODE A/C AMB Ambient Compressor Temperature Sensor Evaporator Blower Speed Temperature Water Resistor Sensor Temperature SensorAutomotive Air Conditioning Training Manual 51
  53. 53. ComponentsElectronic Temperature Control (ECC)Whilst the systems main benefits are attained on the AUTOMATIC mode, the option formanual override exists. But once manual mode has been selected by pushing the fanspeed, A/C or mode switch, it takes away a function normally controlled by the processor inthe ECC module making the processor adjust an alternative component to attain thepre-selected temperature.An additional benefit of the ECC system is a self-diagnostic function which when used willgreatly reduce the time spent locating system faults. IGN Batery + Power 5V Blower Source Motor IGN Circuit 5V Blower Control Reset Fail Blower GND Safe Circuit Control Evaporator Sensor Analogue to Digital Converter Central Processing Unit Output Operation Circuit Input Interface Circuit Ambient IGN Air Mix Water Door Intake Mode Vent In Car Mode Defrost Sun Mode Foot Sensor Water Temp. Compressor ECM A/C Request Input Interface High Blower Speed Request Relay LCD Driver Circuit Light LCD Illumination Key PadAutomotive Air Conditioning Training Manual 52

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