Fog Light Not Working? Here's How to Fix It
Your fog light is out. Maybe one side, maybe both. The good news is fog lights are some of the simplest lights on your car to diagnose and fix. Let's walk through the usual suspects.
Burned Out Bulb
If one fog light is out and the other still works, it's the bulb about 90% of the time. Fog lights sit right behind the front bumper, inches from the road. They deal with water, salt, gravel, and heat constantly. Bulbs don't last forever down there.
Pull the bulb out and check it. A broken filament is obvious on halogen bulbs. If the glass looks blackened or dark, the bulb is toast.
Replacement bulbs cost $10 to $30 for halogen. On most vehicles you can reach the fog light from under the bumper or through the wheel well liner. Some cars make you remove a small access panel. Either way, it's usually a 15 minute job.
Blown Fuse
If both fog lights stopped working at the same time, check the fuse first. The fog light circuit has its own fuse, usually 15A or 20A. You'll find it in the under-hood fuse box or the interior fuse panel. Your owner's manual has a diagram showing which one it is.
Pull the fuse out and look at it. If the metal strip inside is broken, it's blown. Swap in a new fuse with the same amperage rating.
If the new fuse blows right away, there's a short somewhere in the circuit. Don't keep replacing fuses. That short needs to be found and fixed first, or you risk damaging wiring.
Bad Fog Light Relay
The relay is an electrically controlled switch in the fuse box. When you press the fog light button, it activates the relay, which sends power to the lights. If the relay fails, nothing happens when you hit the switch.
Quick test: find the fog light relay (the fuse box lid or manual will tell you which one), then swap it with another identical relay in the box. If the fog lights start working, the old relay was bad.
A new relay costs $5 to $15. Pull the old one out, push the new one in. Takes about two minutes.
Faulty Fog Light Switch
The fog light switch on most cars is either a pull ring on the headlight stalk or a separate button on the dash. These switches can wear out over time, especially the pull-ring type.
A sign the switch is bad: no click or resistance when you press it, or the fog light indicator on the dash doesn't light up at all. If the fuse and relay are both fine, the switch is the next thing to check.
Replacing the switch varies by vehicle. On some cars it's a separate button that pops out easily. On others, it's part of the headlight stalk assembly, which is more involved. Expect to pay $20 to $80 for the part.
Cracked or Damaged Housing
Fog lights live in the danger zone. A kicked-up rock, a parking lot bump, or even just years of road grime can crack the lens or damage the housing. Once water gets inside, the bulb burns out fast and the socket corrodes.
If the lens is cracked but the housing is fine, some people seal it with clear silicone or lens tape as a temporary fix. But moisture will keep getting in. The better move is to replace the assembly.
Aftermarket fog light assemblies run $40 to $150 depending on your vehicle. OEM replacements cost more, usually $100 to $300. Installation is straightforward on most cars since fog lights bolt directly into the bumper.
Wiring and Ground Issues
Fog light wiring runs along the bottom of the car, which means it's exposed to road spray, salt, and debris. Over time, connectors corrode and ground wires go bad.
Check the connector at the back of the fog light. Unplug it and look for green or white corrosion on the pins. Clean corroded pins with electrical contact cleaner. If the connector is really far gone, you can splice in a new pigtail for about $10 to $20.
The ground wire usually bolts to the body or frame near the fog light. Remove the bolt, sand the contact surface clean, and retighten. A bad ground is one of those things that's easy to miss but causes all kinds of electrical weirdness.
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