February 13, 2025

How to Tell if a Relay is Bad in a Car

A car relay device is basically an electronically operating switch. All of the electrical devices of your vehicle are connected to a car relay. When you activate your headlights, push your car horn, or turn on your windshield wipers, you have just used your car relay to help make that happen.

Car relays modify the amount of electricity (or amps) that flow to the various devices of your vehicle after you activate them. They will activate the lower amp circuit or higher amp circuit in order to adjust the amount of electricity. This is important because you wouldn’t want to have your electrical device directly connected to the switch without a relay in between to adjust the amps. Otherwise, you could burn out the electrical device and the wires that are connected to it.

Any system with several electrical devices will definitely have relays because there is so much electricity being transferred around. These levels of energy must be regulated so that all these devices can operate safely.

When is the relay bad?

Each time you activate or deactivate a light, wiper, or other electrical devices in your vehicle, the relay is used and gets worn down a little bit. It takes anywhere from 75,000 to 100,000 switch actions before a relay device goes bad. So, if you turn on your headlights, that is one action. If you turn off your headlights, that is another action.

Don’t worry because it can take many years for a relay device to go bad. But if you notice that one of your electrical devices has stopped working or is performing poorly in your vehicle, then you need to test your relay to verify whether it is responsible or not. The owner’s manual of your vehicle can let you know where the relay is located. In the average vehicle, the relay is positioned under the hood or inside of the fuse panel.

Tips and Steps to Diagnose a bad Relay

Let’s go over the steps of how to test your relay and see whether it is bad. You might want to have a professional mechanic assist you with these steps.

1) You can begin by opening the hood of your car. If the owner’s manual said to access the fuse compartment, then open that. Find the relay device and make sure you can easily access it.

2) Turn the key in the ignition to the “Accessory Position” without starting the engine. Have a second person touch the relay with their hand and keep it there.

3) Turn on the electrical device in your vehicle that is not working. Ask your partner if they feel anything coming from the relay. If they feel clicks coming from the relay, then it means your relay is functional. But if they don’t feel the clicking, then it means your relay is bad.

4) If the relay is bad, remove it from its socket. The ignition must be off during this process. You should be able to just pull out the relay from the socket. Wait a minute and then reinstall the relay. Sometimes removing and reinstalling the same relay will fix the problem. If not, then you’ll need to install a new relay.

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Conclusion

Your relay will slowly wear down over time. As it gets closer to the end of its life, you’ll notice the energy efficiency of your vehicle will decrease. Then your electrical devices will start to wear out faster, including your battery and wiring. It is a good idea to periodically check your relay with a multimeter device to see how strong the electric current is in it. Read the instructions of the multimeter to figure out how many amps are good or bad.

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