How to Replace a Fog Light Relay

Most, but not all, vehicles today come equipped with fog lights. Fog lights were originally intended to aid with vision when there was fog present. For this reason, most manufacturers will typically mount the fog lights in the front bumper, or on the lower valance.

Symptoms of a failing fog light relay include a clicking sound when turned on or improper functioning of the fog lights. The most common location of the fog light relay is in the underhood fuse and relay box. The underhood fuse/relay box can be mounted in any of several different locations under the hood. It can be mounted on either the driver or passenger side, and either the front or rear, of the engine compartment.

Part 1 of 1: Replacing a fog light relay

Materials Needed

underhood fuse/relay box

Step 1: Locate the underhood fuse/relay box. Open the hood and locate the fuse/relay box. Manufacturers will typically label the box with the word “Fuse” or “Relay” on the lid.

picture of mechanic removing the underhood fuse relay box cover

Step 2: Remove the underhood fuse/relay box cover. The lid of the fuse/relay box can usually be removed by hand, but sometimes a small screwdriver may be necessary to gently pry the retaining tabs back to release them.

picture of fuse relay diagram underhood

Step 3: Identify the fog light relay to be replaced. Identify the fog light relay that needs to be replaced. Most manufacturers will provide a diagram on the lid of the underhood fuse/relay box that will show the location and function of each fuse and relay located inside the box.

removing the relay by hand

Step 4: Remove the fog light relay to be replaced. Remove the fog light relay that needs to be replaced. This can typically be done by pinching it between your fingers and pulling it up and out, or by using a pair of pliers.

It is not uncommon to need to wiggle it back and forth while pulling on it.

  • Note: You can also use a small screwdriver to gently pry a fuse or relay from its position, as long as you are very careful not to make contact with the metal terminals on them. This can cause a short and lead to additional issues.

Step 5: Match the replacement fog light relay to the original. Visually compare the replacement fog light relay to the one being removed. Be sure it has the same basic dimensions, the same amperage rating, and that the terminals are in the same number and orientation.

new relay being installed

Step 6: Insert the replacement fog light relay. Line up the replacement fog light relay with the recess the old one came out of. Gently set it in place and push down until it stops. The base should be flush with the fuse box deck and be approximately the same height as the relays around it.

Step 7: Reinstall the underhood fuse/relay box cover. Place the underhood fuse/relay box cover back onto the fuse/relay box and push down on it until it engages the retaining tabs. There should be either an audible click when it engages, or a felt click.

Step 8: Confirm replacement of the fuse relay. Once everything has been reinstalled, turn the ignition to the “run” position. Turn the fog lights on and verify the fog lights’ operation.

Although fog lights are considered more of a convenience item, rather that a safety item, in areas where fog is a more common occurrence, fog lights can provide a better and safer driving experience.If at any point in the process you feel you could use a hand replacing a fog light relay, contact a professional technician, such as those available at YourMechanic. YourMechanic has trained and certified professionals that can come to your home or place of business and perform the repairs for you.


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