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# Wire Harness Test Simple

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a very basic presentation for simple testing

a very basic presentation for simple testing

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### Transcript

• 1. 1
Testing a Wire Harness
Ronald Spohrer
• 2. 2
Overview
Two methods of testing a harness using a Multimeter
• The Ohmmeter
• 3. The Voltmeter
• 3
Safety Reminder
Before testing any circuit, remember personal safety and equipment
Wear Glasses, hearing , and gloves
Working with electricity, it is possible for:
Shock
Arcing
Burns
• 4. 4
Testing with an Ohmmeter
Test meter to make sure it is working
Isolate the component or segment of the circuit that is to be tested
Set the meter on the Ohm Scale.
Hint: Look for the upside-down horse shoe
• 5. 5
Ohmmeter
Remove the current (power/voltage)
How:
At the source by removing the fuse
Turning off the ignition switch, that is if the circuit is controlled by the switch
Disconnect from the power source, battery
• 6. 6
Ohmmeter
One at the start or beginning of the circuit and the other at the end
If there is continuity (no break) the meter will show zero or low resistance.
That is 000 or possibly a few ohms of resistance depending on the length of wire, connections, and number of devices in line.
• 7. 7
Ohmmeter
If there is a break or open wire the meter will read 1. or UL
If there is a break:
Keep moving from the end back to the source to isolate the break
Check each connection that is in line on that circuit
• 8. 8
• 9. 9
Testing with a Voltmeter
Test the meter make sure it is working
Set the meter to the DCV scale matching the circuits voltage and the vehicles
This could be 6v, 12v, 24v, 36v, 48v, 120v.
• 10. 10
Voltmeter
Attach the negative probe, the black lead, to the ground of the vehicle
Using the positive probe, the RED lead,
Start at the source of the circuit
Check for voltage working from the beginning to the end of the of the circuit
• 11. 11
Voltmeter
Example:start at the beginning and progress to the end of the circuit
Battery
Master switch
Ignition switch
Fuse
Connections
The end may be a light
• 12. 12
Voltmeter Safety Cautions
Leave the ground lead (negative lead) connected at all times to a good clean spot
When the circuit is energized, it may move a function of the machine
Always a possible shock hazard
• 13. 13
Voltmeter
If voltage (power, current) is to and through the light or end use device, but still not working, then most likely the problem is in the ground side of the circuit.
If possible, check the ground connections
Are they clean, tight, and in good state of repair?
Replace the connection or wire as needed
• 14. 14
• 15. 15
Testing the Wiring Harness
The wiring harness is the main branch with which electrical needs of a machine and its components are met
Wires are commonly sheathed to protect
Wires emerge at points along the frame for usage as needed by the machine
• 16. 16
Wire Harness
If a bad wire is found:
Individual wires can be repaired or replaced as needed
Replace a wire by cutting off the ends of the defective wire and discard
Run a new wire along and attach with plastic clips and electrical tape
• 17. 17
Wire Harness
Always use the same size wire.
A smaller wire will not carry the load and in turn will overheat or melt.
Do not attempt to thread a new wire into the harness as this may damage other wires in the harness.
• 18. 18
Wire Harness
Electricity needs a complete circuit to follow
It will take the path of least resistance
When testing a harness one needs to move the harness around when testing with your meter connected
• 19. 19
Wire harness
Test for open wire (broken wire)
A-D } infinite resistance
A-C } infinite resistance
A-B } infinite resistance
• 20. 20
Wire Harness
Tests for short
Bare wire touching frame
A-D} zero
A-C} infinite
A-B} zero if wire intact but grounded
A-B} infinite if wire is broken but not touching ground
• 21. 21
Wire Harness
Testing for short, two wires touching
A-C} zero
A-B} zero
A-D} zero if wires touching frame
A-D} infinite if wires are not touching frame
• 22. 22
• 23. 23
Blown Fuses
Not always a short
(ice in fan, too many added on devices)
Incorrect fuse size
Poor contacts - pitted, corroded, excessive resistance
• 24. 24
Remenber
Need to stress check grounds
Clean, tight, free of corrosion
One major reason, more and more plastic being used
Probe at the connection not the wire, every extra hole in wire a place for future problems
Personal safety and equipment
• 25. 25
In review
Two methods of testing a harness using a Multimeter
The Ohmmeter
The Voltmeter