How to Test a Flasher Relay

by Ashton Daigle
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12 volt relais, relay image by Sascha Zlatkov from

Emergency flashers are essential safety features in our cars or trucks. Flashers, or hazard lights, are controlled by a flasher relay, an plug-in electrical device. If your flashers begin to blink quickly or erratically, there's a good chance the relay is going bad and it should be tested. Testing the flasher relay is a straightforward task that should take you about 15 minutes.

Step 1

Access the junction box where your flasher relay is located. The location of the junction box that holds the flasher relay will depend on the make and model of your vehicle. In some models, it is located in the engine compartment near the battery. On other models it is located near or in the steering wheel column. Consult your owner's manual to pinpoint its location, then open the junction box.

Step 2

Turn your car or truck's ignition on.

Step 3

Connect the clip of the test probe to any good ground. Probe the main wire leading from the relay with the test light. if the bulb lights, it means the relay is working.

Step 4

Remove the relay and locate its control and power terminals.

Step 5

Turn your multimeter on and set it to the ohms setting. Place the meter's test wires across the power and control terminals. No continuity should register. If the relay reflects continuity, replace it.

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