How to Test a Relay Switch

Wherever you find devices or vehicles that are operated by electricity, you will find a relay switch. Used as a safeguard to prevent electrical overloads, these switches open and close when given an electronic signal. It's kind of like a traffic signal for electricity to make sure the current is sent to the right place. But how do you know if your relay switch is working properly? By using a testing meter, you will be able to verify whether your switch is operating efficiently or if it needs replacing.

Things You'll Need

• Electrical testing meter (2) Fused jumper wires about 2 feet long

Instructions

How to test a relay switch

1. Locate the switch that you would like to test. Turn ignition switch on without starting engine and use the test meter to verify the switch in question is receiving power.

2. Unplug switch relay from electrical harness and locate power and control terminals on switch. Connect larger wires from test meter to the power terminals and smaller wires to the control terminals. Refer to vehicle owner's manual for information on relay terminals.

3. Check continuity of the power relay terminals with test meter. If the terminals test positive, you need to replace the relay switch.

4. Check the control terminals by running a fused jumper wire from a control terminal to the positive terminal of your car battery. By connecting your second jumper wire to the remaining control terminal, you should hear a clicking in the relay switch. If no clicking is heard, the relay switch needs to be replaced.