What You Need to Know About Malfunctioning Headlight Relays

What You Need to Know About Malfunctioning Headlight Relays

Tajinder Kalia

The headlight relay is a small but important part of a modern vehicle. It helps control the high beams and the low beams of your car. When the relay does not work correctly, then the headlights may not turn on at the same time. That creates a safety hazard, which is why it is crucial to address the problem as soon as possible.

What Are Headlight Relays For?

When the headlights are on, the low beams are on. The high beams come on when the relay opens, and they remain on until the relay switch is shut off again. The headlight relay is meant to protect the electrical system on your vehicle. It is always placed in a position where it is easy to reach but not where it is likely to get submerged in water.

You can check the headlight relay on your vehicle by performing a voltage drop test. First, unplug the relay and test the power coming to the relay. Then, connect the relay and test the voltage delivered to the working lights. If the voltage drops, then you know that the relay is shorted.

Symptoms of a Bad Headlight Relay

If the headlights do not come on simultaneously, you should suspect that the relay switch is defective. There are two possibilities. The relay could be bad, or the wiring could be faulty. If the wiring is faulty, you will need to track down the problem. A typical relay switch may also have a problem with the contacts. That means that you will have to replace the relay. 

Here are some common signs that your headlight relay may have a problem.

1 – The Headlights Do Not Turn On

If your headlights do not come on when you turn the ignition key to start the engine, the problem is most likely with the fuses. Check the fuses if they have blown. The headlights should come on as a secondary function when the engine comes on. The headlights should also turn on when you press the high beams of the switch.

2 – The High Beams Do Not Turn Off

If the high beams do not turn off when they should, the relay is not working. If the low beams are set automatically when the high beams are turned on, then the relay is probably bad. It could also be that the wiring is failing.

3 – The Concealed Headlights Don’t Work Properly

Concealed headlights are very useful in some situations, but they don’t always work the way they should. If the high beams are not coming on, you need to check the relay. The headlights may not be working properly if you have problems with other systems on your vehicle.

How Do You Repair a Headlight Relay?

If your headlights are not working as they should, then you can inspect the wiring and replace the relay as needed.

Fixing a headlight relay is a straightforward process. You have to open the hood, locate the relay, and trace the wires. Then, you will be able to determine if the wiring needs repair or the relay itself.

If you are not a skilled mechanic, then you may want to have a mechanic do the work for you. As with any vehicle repair, it is best to get professional assistance if you are not an experienced mechanic. If you have questions, consult a professional to ensure that your vehicle is repaired correctly.


If your headlights are not coming on when they should, you probably have a problem with the relay. You can check the relay, and you can also check the wiring. If the wiring is not faulty, you will need to replace the relay. Acting on it promptly can help you avoid serious problems in the future.

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