How To Test a Starter Relay


how-to-test-a-starter-relay A starter relay may be bad if you see the following symptoms

  • An engine that won’t start at all( remains silent even after you turn on the ignition key)
  • You hear multiple clicks but without the engine starting
  • The starter relay remains on even after you have turned the ignition key off
  • The ignition key needing to be turned on and off some times for the engine to start( intermittent starts)

The above symptoms may be as a result of a bad starter relay, or the problem could be with connections that have worn out and are not sending enough current to coil in the starter relay.

Still, it could be a case of a failing battery that’s not sending enough current and that needs to be replaced or charged. To find the cause of the problem, you would need to carry out a series of tests on the starter relay circuitry.

Testing a starter relay is fairly simple because of its position in the engine bay. You do not need to lift the car or to dismount many parts. And, you only need a few tools.

Materials You Will Need

  • A digital multimeter
  • A piece of wire to act as a jumper
  • Wrenches and a ratchet & socket set( in case you will need to remove the starter relay, or dismantle anything else)

Testing The Starter Relay

Before you begin with the tests, find a working battery that’s fully charged. Or you can test the available battery to ensure it’s at 12V and is not the source of the problem. Once you’re done with checking the car battery, disable the engine so that things don’t move while you’re working.

The Testing Procedure

Find starter relay you suspect to be bad. You will easily find it near the battery and has the battery’s positive terminal wire connected to it.

Have a helper turn on the ignition switch while you listen to the noise the starter relay makes. If turn on the ignition switch, there’s a single or a series of weak clicks, you will have to test it for electrical resistance. If the sound is a single strong click, you should check the starter relay for voltage drop.

  1. Testing For Electrical Resistance

  • Set your multimeter to be on the Ohms scale. Place one probe on the lead on the ignition circuit terminal and the other on the ground lead. The reading should be less than 5 Ohms. If it’s more than that, the starter relay is faulty and needs to be replaced.
  • You can also check for resistance by placing the red probe of your multimeter to the ignition circuit terminal and the other to the ground terminal. If the voltage you read is not 12V when the ignition switch is turned on, the starter relay is faulty.
  • Another way to test for resistance by use of a wire jumper. Connect the wire between the battery lead and the ignition circuit lead. A strong click from the starter relay shows its working while a series of weak click or a single weak click show its bad and needs replacement.
  1. Testing For Voltage Drop

  • Set the multimeter to 20V DC
  • Place the red probe of your multimeter on the terminal connection of the red wire from the battery.
  • Place the other probe on the connection leading to the ignition switch circuit( the black and thin wire)
  • Ask your helper to turn on the ignition as you read the multimeter. The voltage drop should be no more than 0.2V.

If it’s more than that, there’s a problem with electrical conductivity to the starter relay which needs to be addressed. You would need to inspect the leads and clean them out.

If even after cleaning the terminals the reading remains high, the starter relay needs to be taken out and replaced with a new one.

In Summary

Testing a starter relay helps you to diagnose the problem that’s making the car not to start. Starter relays do fail. They’re small components but make the primary circuit that supplies power to the main starter system. If they don’t work properly, your car cannot start.

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