Electric Motor Testing & Troubleshooting

Written by dan ferrell
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Electric Motor Testing & Troubleshooting
Electric motors come in different sizes and designs, which make them ideal for automotive use to power windshield wipers, antennas and rear view mirrors. (Photo courtesy of Orgullomoore at Commons Wikimedia.org)

The use of electrical motors in vehicles is very common and useful. These small wonders are capable of converting electrical energy into mechanical energy to power windshield wipers, windows, antennas, seats and rear view mirrors. Electrical motors make you safer on the road, however they are not infallible. Follow these simple steps to troubleshoot and test any electrical motor in your vehicle before you blame it for a power failure and rush to replace it. Let's go.

Skill level:
Moderately Easy

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Things you need

  • Ohmmeter
  • Test light
  • 2 jumper wires

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Instructions

  1. 1

    Check the fuse for the circuit you need to test. For example, if your power windows do not work, check the main fuse for the power windows.

  2. 2

    Pull out the fuse and look at the metal strip. If the strip is broken replace it. Also check for continuity with an ohmmeter. Set the ohmmeter for the lowest ohms range or continuity setting and touch each of the fuse spade connectors with the probes. If the resistance reading is infinite or there is no beeping sound coming from your ohmmeter, replace the fuse.

  3. 3

    Check the wire going from the fuse to the circuit switch for continuity. Using a test light, connect the alligator clip at the end of the test light wire to ground. Turn on the power to the circuit you are testing and touch the light probe to the wire coming from the fuse panel at the switch. If the light does not come on, there is a shortage in that side of the circuit. Turn off the power.

  4. 4

    Pull the switch and test it for continuity with the ohmmeter as described on step 2. Make sure to operate the switch on and off. If there is no continuity, replace the switch.

  5. 5

    Test for incoming voltage at the electric motor. Connect your test light to a good ground, turn on the power to the circuit and touch the test light probe to the wire coming from the switch at the electric motor and turn on the switch. If the test light does not come on, there is a shortage in the wire.

  6. 6

    Test the electric motor ground connection. Using a jumper wire, connect one end to a good ground and the other to the electric motor ground terminal. Turn on power to the circuit. If the motor works now, make sure there is a good ground connection at the motor and check for a possible short at the ground wire. Turn off the power.

  7. 7

    Disconnect the electric motor. Using a couple of jumper wires, connect the electric motor directly to battery power. If the motor works now, there is a problem with the connections providing power to the electrical motor. If the motor does not operate, replace it.

Tips and warnings

  • You can start troubleshooting at any point in the circuit that is more accessible to you. You can start at the switch for example. If your results are negative, work your way back towards the power source to find the problem. If you register power at the switch, follow the circuit towards the motor to find the problem.
  • You can consult your vehicle service manual to locate and identify wires and components for testing. You can buy a service manual at most auto parts stores or consult one for free at your local public library.

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