Headlight Relay Location: a Comprehensive Guide
Electric System

Headlight Relay Location: a Comprehensive Guide

If the headlights on your vehicle are not working correctly, you may be dealing with a damaged or failed headlight relay. A headlight relay is an electric switch located in the wiring harness of most modern vehicles and is used to control the power flow to the vehicle’s headlights. The relay lowers the voltage of the electrical current that powers your headlights so that they are bright enough to see without causing damage to other components in your car or truck. In this comprehensive guide, you’ll learn all about headlight relays, including their location and purpose, and what you should do if you have a failed headlight relay.

What Is a Headlight Relay?

Headlight Relay Location - A Comprehensive Guide A headlight relay is an electrical device housed in a metal box that consists of two separate circuits: one for high-beam headlights and another for low-beam headlights. When activated, the relay will open and close these two circuits at predetermined intervals, thus controlling how much power each circuit receives from the battery. In some cases, there may be more than one headlight relay depending on how many sets of headlights are installed in your vehicle (for example, fog lights). All relays have a coil wound around them, which creates an electromagnetic field when activated by an electric current from the battery – this allows it to open and close circuits when needed.

Headlight Relays Location

Headlight relays are located next to the headlights, usually near the front of the vehicle. They may be mounted in various areas, such as behind the headlights, in the engine bay, or under the hood. In most vehicles, headlight relays will be found in a compartment behind each headlight assembly. This compartment houses several electrical components and is usually located on either side of the radiator core support or near the hood latch. To access these compartments, you’ll need to remove some panels and screws that secure them to their location. Once inside, you can locate and remove your headlight relays. Also read about Best Aftermarket Headlights for Ford Super Duty.

Common Problems with Headlights

Headlight problems can range from dim headlights to flickering lights. In most cases, these issues can be traced back to a failed headlight relay. If the relay is not working correctly, it can cause several problems, such as an increase in electrical resistance (which causes dim headlights), a decrease in voltage (causing flickering lights), or even complete failure of the lights when the relay cannot open and close circuits properly. Additionally, if your car or truck has multiple headlights, you may experience problems only with one set due to a faulty headlight relay.

How to Troubleshoot a Failed Headlight Relay

Headlight Relay Location - A Comprehensive Guide If you suspect that your headlight relays are not functioning correctly, there are several steps you can take to troubleshoot and diagnose the issue. First, check for any broken wires or loose connections at both ends of the relay – this will indicate an open circuit somewhere in the wiring harness. You may also want to inspect for corroded contacts on the relays themselves, as this could prevent them from connecting correctly with other components in your vehicle’s electrical system. Once you have identified and addressed any physical issues with the relays, test them using an automotive multimeter by connecting one end to each terminal of the relays. If it reads 0 ohms, your relays should be working correctly, and no further troubleshooting is necessary. If it reads anything other than 0 ohms, you will need to replace your headlight relays before they start working again.


Headlight relays are an important component of any vehicle’s electrical system, as they help to protect other components from damage and provide the power necessary for your headlights to function correctly. If your headlights are not working as expected, you likely have a faulty headlight relay. In this comprehensive guide, you’ve learned all about the location and purpose of headlight relays and how to troubleshoot a failed one. With this knowledge, you should now be able to identify any problems with your headlight relays and replace them if necessary to get back on the road safely.