Chapter 51

[object Object],[object Object],[object Object],OBJECTIVES: After studying Chapter 51, the reader should be able to: Continued

[object Object],[object Object],OBJECTIVES: After studying Chapter 51, the reader should be able to: Continued

BLOWER MOTOR SERVICE ,[object Object],Continued ,[object Object],[object Object]

COOLING SYSTEM SERVICE ,[object Object],[object Object],Continued Figure 51–1 Some heater hoses are best inspected by hoisting the vehicle and inspecting them from underneath the vehicle as shown.

[object Object],Heater hoses are designed to supply warm coolant from the engine’s cooling system to the small radiator called the heater core inside the vehicle. Because the heater hoses attach to the engine and the engine moves on its mounts during operation, the heater hoses are long enough to allow the engine to move without causing stress to be applied to the heater core. The extra length also helps to prevent engine vibration from being transmitted to the heater core and the interior of the vehicle. When replacing heater hoses, always use the old hoses as a guide and use the same length hoses. Also, route the replacement hoses in the same manner as originally designed, again, to help reduce the stress to the heater core. Use the Same Length Heater Hoses

The air dam under the front of the vehicle is designed to force air to flow upward and through the radiator rather than travel underneath the vehicle. If this air dam is broken or damaged due to contact with a parking block or other object, the engine may overheat. Check the Air Dam if Overheating Occurs

REFRIGERANT RECOVERY PROCEDURES ,[object Object],Continued

Figure 51–2 (a) A typical automotive air-conditioning service machine that is capable of handling both CFC-12 and HFC-134a systems. (b) HFC-134a systems use quick-disconnect fittings that are larger than those used for CFC-12 systems.

[object Object],Figure 51–3 (a) Refrigerant oil must be retrieved and measured when the refrigerant is recovered from the system. (b) A rubber O-ring is used to indicate the level of refrigerant oil already in the container. The exact same amount of refrigerant oil must be installed as was removed when the system is recharged. Continued

[object Object],Continued NOTE: Be sure to follow all instructions regarding the amount of oil that needs to be added to the system if components have been replaced.

[object Object],Continued ,[object Object],[object Object],[object Object],The O - ring seal is part of a fitting that holds the ends of two refrigerant lines or hoses together inside a connector. O-rings form the seal between the lines or hoses and the connector. O-rings are made of highly saturated nitriles (HSN) or neoprene rubber and remain flexible over a wide range of temperatures. The O-ring must be lubricated with clean refrigerant oil before assembly to ensure a good seal. Be careful not to crimp the O-ring during installation.

Figure 51–4 O-rings are usually made of neoprene rubber or highly saturated nitriles (HSN) to withstand high temperatures and flexing. O-rings should be changed during a retrofit procedure. ,[object Object],Continued

[object Object],Figure 51–5 A Ford spring-lock coupling. Continued It uses two O-rings mounted on the small end of the refrigeration line.

[object Object],Figure 51–6 A special tool is needed to remove and install the Ford spring-lock coupling. Continued

[object Object],Figure 51–7 The service cap O-ring becomes the primary seal if the service valve leaks. Continued

[object Object],Figure 51–8 A depressor pin on the gauge set opens the Schrader valve when the connection is almost completely tightened. This prevents accidental refrigerant discharge. When the service connection is made, the depressor in the end of the service hose or service coupling, presses on a small pin inside the valve, forcing the valve open. The high-side service valve on R-12 systems is smaller and has different threads than the low-side valve.

Always wear safety glasses and protective gloves when servicing any automotive air-conditioning system. If refrigerant escapes, it can freeze skin or cause blindness if liquid refrigerant were to get into the eyes. Refrigerant Can Be Hazardous

EVACUATION PROCEDURES ,[object Object]

[object Object],A typical vacuum gauge reads in inches of Mercury (in. Hg) and the recommended vacuum level needed to remove moisture from the system is considered to be 27 in. Hg or less. However, many experts recommend using a vacuum gauge that measures the amount of air remaining in the system. This type of gauge measures vacuum in microns. A micron is one millimeter of a meter and there are about 760,000 microns of air at atmospheric pressure. A vacuum reading of 29.72 in. Hg is about 5,000 microns. Many experts recommend that the micron level be 500 or less for best results. Use a Micron Vacuum Gauge for Best Results Figure 51–9 An air-conditioning vacuum gauge that reads in microns.

NONCONDENSIBLE GASES ,[object Object],[object Object],[object Object],If the only contaminate is air, it can be purged from the refrigerant. If air is present in the container of refrigerant, it is considered to be a contaminate and will reduce the cooling efficiency if installed into an air-conditioning system. There are two ways to determine if there is air (noncondensable gas) in the refrigerant, including:

REFRIGERANT RECYCLING ,[object Object],Continued ,[object Object],[object Object],[object Object]

Figure 51–10 A typical under-hood sticker identifies the refrigerant and the amount needed to change the system in kilograms (0.96 kg is equal to 0.44 pounds). ,[object Object],Figure 51–11 A temperature and humidity gauge is a useful tool for air-conditioning work. The higher the relative humidity, the more difficult it is for the air-conditioning system to lower the temperature inside the vehicle. RECHARGING A SYSTEM

[object Object],The Cadillac Story The tech then remembered that if a diagnostic trouble code (DTC) has been set, the computer will not allow the compressor clutch engage.This is a precaution to prevent compressor damage if the system is low on charge and not able to transfer lubricating refrigerant oil through the system the compressor needs for lubrication. The tech disconnected the negative (+) battery cable, waited several minutes and then reconnected it. After starting the engine and turning on the A/C controls, the compressor clutch engaged and the service technician was able to complete charging the system.

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Many air-conditioning systems use orifice tubes that look similar if not identical. They are usually color coded for identification. Always use the recommended orifice tube for the vehicle you are servicing. Some examples of the various colors and sizes available include: Because It Fits, Does Not Mean it is Correct! Make Color Orifice Size (Inches)

[object Object],RETROFITTING A CFC-12 SYSTEM TO A HFC-134A SYSTEM Continued ,[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Continued

[object Object],Figure 51–12 (a) When a system is retrofitted from CFC-12 to HFC-134a, the proper service fittings have to be used to help assure that cross-contamination does not occur. (b) An under-hood sticker is also installed indicating that the system was retrofitted to HFC-134a and when it was done and by whom.

COMPRESSOR SERVICE ,[object Object],Continued Figure 51–13 A special tool is needed to remove and install the magnetic clutch on the air-conditioning compressor. Compressor Clutch Service If the compressor clutch is blue, it indicates excessive heat generated by the slipping clutch. Replace the clutch and adjust the air gap according to service information instructions.

[object Object],Continued Step #1 Remove the refrigerant from the system. Step #2 Disconnect the compressor drive belt. Step #3 Disconnect sensors and compressor clutch wiring connections and label them if needed. Step #4 Disconnect the suction and discharge hoses. Step #5 Seal the hoses to help keep moisture and dirt from entering the system. Step #6 Remove the compressor mounting fasteners. Step #7 Drain and measure the refrigerant oil from the compressor. Step #8 Inspect the hose, lines, fittings, O-rings, seals, muffler, and service valves for proper operation and repair or replace as needed as part of the compressor service.

If the air-conditioning compressor is found to be damaged mechanically, many experts recommend that an additional filter be installed in the refrigerant line to trap any debris that may have gotten into the system. This additional filter will help prevent the new compressor from being harmed by the debris as it circulates through the system. An Additional Filter is Insurance

CONDENSER SERVICE ,[object Object],Figure 51–14 A fin comb is used to straighten the fins on the condenser to help increase airflow and heat transfer.

EVAPORATOR SERVICE ,[object Object]

[object Object],RECEIVER/DRIER OR ACCUMULATOR/DRIER SERVICE Continued Figure51–15 Always be sure that the service valves are snug before evacuating the system. They are a common place for small refrigerant leaks.

Whenever an evaporator is being replaced, many service technicians also recommend that the heater core also be replaced. This is especially true if the vehicle had a neglected cooling system. Most heater cores are close to or even have to be removed to replace an evaporator. The only additional cost to the vehicle owner is the cost of the heater core itself. Might As Well Do It Now

ORIFICE TUBE/EXPANSION VALVE SERVICE ,[object Object]

SUMMARY ,[object Object],[object Object],[object Object],[object Object],Continued

SUMMARY ,[object Object],[object Object],( cont. )

Chapter 51

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Chapter 51