How to Test Starter Relays

by Dan Swords
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The starter relay and the neutral lockout switch control the starting solenoid. These two components work together to ensure that the starter operates safely and does not turn the engine over in an unsafe condition. The starter relay provides power to the starter when the key switch is turned to “Start.” The starter relay acts like an electrical switch routing battery voltage to the starter when it receives a signal from the key switch.

Step 1

Inspect the battery and starter terminals. Verify that they are free of corrosion, oil dirt and debris. Before cleaning corroded terminals, disconnect the minus batter cable and place it off to the side. Disconnect the positive battery cable and place the cable off to the side. Make sure the cables will not accidently touch the battery terminals. Clean corroded terminals with baking soda, water and a wire brush. If required, clean the starter terminals. Leave the battery cables disconnected.

Step 2

Follow the wires from the starter solenoid to the starting relay. There are four terminals on the relay. The two smaller wires come from the key switch circuit and are used to turn the relay “On.” The two larger wires route battery voltage from the battery to the starter. Mark the two smaller wires so they can be reconnected properly and then remove the wires from the starter relay. Use a jumper wire and connect one end to chassis ground. Connect the other end to terminal 86.

Step 3

Connect a jumper wire to the positive battery post. Since the battery connection to the starter has been disconnected, it is okay to leave the jumper wire connected for a short time. Use a digital voltmeter to measure the resistance between terminals 30 and 87. The resistance should be less than one ohm. If the resistance is greater than one ohm, the relay is not working properly. Replace the relay.

Step 4

Reconnect the battery and key switch connections to the relay. Reconnect the positive battery cable. Once it is secure on the battery post, reconnect the negative battery cable.

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