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1<br />Testing a Wire Harness <br />Ronald Spohrer<br />
2<br />Overview<br />Two methods of testing a harness using a Multimeter<br /><ul><li>  The Ohmmeter
  The Voltmeter</li></li></ul><li>3<br />Safety Reminder<br />Before testing any circuit, remember personal safety and equ...
4<br />Testing with an Ohmmeter<br />Test meter to make sure it is working<br />Isolate the component or segment of the ci...
5<br />Ohmmeter<br />Remove the current (power/voltage)<br />How:<br />At the source by removing the fuse<br />Turning off...
6<br />Ohmmeter<br />Connect the probes or leads<br />One at the start or beginning of the circuit and the other at the en...
7<br />Ohmmeter<br />If there is a break or open wire the meter will read 1. or UL<br />If there is a break:<br />Keep mov...
8<br />
9<br />Testing with a Voltmeter<br />Test the meter make sure it is working<br />Set the meter to the DCV scale matching t...
10<br />Voltmeter<br />Attach the negative probe, the black lead, to the ground of the vehicle<br />Using the positive pro...
11<br />Voltmeter<br />Example:start at the beginning and progress to the end of the circuit<br />  Battery<br />  Master ...
12<br />Voltmeter Safety Cautions<br />Leave the ground lead (negative lead) connected at all times to a good clean spot<b...
13<br />Voltmeter<br />If voltage (power, current) is to and through the light or end use device, but still not working, t...
14<br />
15<br />Testing the Wiring Harness<br />The wiring harness is the main branch with which electrical needs of a machine and...
16<br />Wire Harness<br />If a bad wire is found:<br />Individual wires can be repaired or replaced as needed<br />Replace...
17<br />Wire Harness<br />Always use the same size wire. <br />   A smaller wire will not carry the load and in turn will ...
18<br />Wire Harness<br />Electricity needs a complete circuit to follow<br />It will take the path of least resistance<br...
19<br />Wire harness<br />Test for open wire (broken wire)<br />A-D } infinite resistance<br />A-C } infinite resistance<b...
20<br />Wire Harness<br />Tests for short <br />Bare wire touching frame<br />A-D} zero<br />A-C} infinite<br />A-B} zero ...
21<br />Wire Harness<br />Testing for short, two wires touching<br />A-C} zero<br />A-B} zero<br />A-D} zero if wires touc...
22<br />
23<br />Blown Fuses<br />Not always a short<br />Possible temporary overload<br />   (ice in fan, too many added on device...
24<br />Remenber<br />Need to stress check grounds<br />Clean, tight, free of corrosion<br />One major reason, more and mo...
25<br />In review<br />Two methods of testing a harness using a Multimeter<br />The Ohmmeter<br />The Voltmeter<br />
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Wire Harness Test Simple

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a very basic presentation for simple testing

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Wire Harness Test Simple

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

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