The Headlight Relay: What You Need to Know

The headlight relay is responsible for controlling the power that the headlights receive from the car’s battery. Over time, this relay can start to wear down, making it difficult for your car’s headlights to work properly. It is important for drivers to understand the purpose of the headlight relay and how to identify problems with it so that they can keep their cars running in top shape.

In this post, we will explain what a headlight relay is, how it works, where it is located, and what you need to do if you suspect that your vehicle’s headlight relay is having an issue.

What is a headlight relay?

A headlight relay is a small electrical device found in most vehicles. It’s typically situated in the power distribution centre of your vehicle, and its purpose is to control the current that flows to the headlights. The relay works by using a low-amperage current from the switch to control the larger current of the headlights, ensuring that the correct amount of power is delivered to the headlights without causing any damage. 

Can a headlight function without the relay?

For those who are wondering “where is the headlight relay, can a headlight function without it and what have you?”, the answer is that it is usually located in the engine compartment and just maybe your headlight can function without it, let’s find out. Even if you can’t find the headlight relay, it doesn’t mean that your headlights won’t work. In fact, many modern cars have headlights wired directly to the battery, so they can still turn on even without the relay. However, without the relay, the headlights may not be as bright, and you may also be at risk of draining your battery. 

The function of the headlight relay 

The headlight relay is a critical component of your car’s lighting system and its primary function is to control the operation of the headlights. The relay works by allowing a low current of electricity to operate the headlights, thus ensuring that the headlights don’t overheat and burn out.

In addition, the relay can be used to turn the headlights on and off according to the user’s preference. When you’re asking yourself “Where is the headlight relay?” first understand what it does and how it operates.

Understanding your headlights

How to locate the headlight relay quickly and easily

Another step in understanding the headlight relay is locating it quickly and easily. This is an important step, as it allows you to quickly get the lights working again if they have stopped working. To locate the headlight relay, do the following:

  • First, look in the fuse box. The headlight relay is usually found in the same area as the fuse box. 
  • If it’s not in the fuse box, look near the battery, as this is also a common location for the headlight relay. 
  • If you still can’t find it, you can consult your car’s manual or an online resource to help you identify exactly where it is located. 

How do you diagnose and fix a bad relay?

When it comes to diagnosing and fixing headlight relay problems, the first step is locating the headlight relay. This will usually be found in either the engine bay or inside the vehicle cabin, depending on your make and model as explained above.

Once you’ve located the relay, it’s important to check for any signs of visible damage, such as corrosion, to ensure that the relay is functioning properly. If the relay is clearly damaged, it should be replaced. If the relay appears to be in good condition, you can use a multimeter to check the current output. And if the output is too low, then it’s likely that the relay has failed and should be replaced.


The headlight relay is an important component of your vehicle’s lighting system. It ensures the headlights are always powered and the bulbs do not burn out prematurely. If your headlights are not working correctly, it is important to check the relay and make sure it is in good working condition. Replacing a faulty relay is relatively simple and is a job anyone can do at home with basic tools, hence the importance of knowing where the headlight relay is. 


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