How to Replace a Fog Light Bulb or Unit (Step by Step)

Short answer: to replace a front fog light bulb, reach the back of the light through the wheel arch liner or from underneath the bumper, twist out the bulb holder, swap the bulb and refit. To replace the whole unit, remove the fixings, disconnect the wiring plug and fit the new unit. A rear fog light is usually part of the rear light unit, so you replace its bulb the same way as a tail light bulb. Access varies a lot between cars, so check your owner’s manual first.

This guide covers both jobs, plus what to check before you start and after you finish.

Before you start

• Find your bulb type. Your owner’s manual lists it, or you can check the old bulb once it’s out. Some fog lights use a halogen bulb, and some have built-in LEDs.
• Make sure you have the right part. If you’re replacing a whole unit, match the model, year, side and position. Our guide on how to check headlight compatibility was written for headlights, but the same steps apply to fog lights.
• Gather basic tools. Usually a screwdriver or a Torx or socket set, a trim removal tool and a cloth.
• Switch off the lights and the ignition, park on level ground and let the bulb cool if it was on recently.

How to replace a front fog light bulb

1. Find the access route. On many cars you reach the back of the fog light through a gap behind the bumper. You may need to turn the steering to one side, and remove a section of the wheel arch liner or an under-tray. Your manual or a model-specific guide will show you.
2. Disconnect the wiring connector from the back of the bulb holder, if it’s separate.
3. Remove the bulb holder. Most twist a quarter turn anticlockwise and pull out. Some have a small clip.
4. Remove the old bulb. Pull it straight out, or push and twist, depending on the type.
5. Fit the new bulb. Halogen bulbs shouldn’t be touched on the glass with bare fingers, because skin oil can shorten their life. Hold it by the base or use a clean cloth.
6. Refit the holder and plug the connector back in.
7. Test it before you refit anything else: switch on the dipped headlights, then the fog lights.
8. Refit the liner or under-tray.

How to replace a whole front fog light unit

1. Gain access as above. On some cars you’ll need to remove the front grille section, the under-tray or part of the bumper trim.
2. Disconnect the wiring plug. Take a photo first if the connectors look similar.
3. Remove the fixings. Most units are held by screws or bolts, and some by clips or tabs.
4. Ease the unit out from the front or behind. Check for a hidden clip before you force it.
5. Transfer what you need. If the replacement doesn’t include the bulb or holder, move them over from the old unit.
6. Fit the new unit, line it up and tighten the fixings evenly.
7. Reconnect the plug and test.

How to replace a rear fog light

On most cars the rear fog light is part of the rear light unit or fitted in the bumper. If it’s in the rear light unit, replace the bulb the same way as a tail light bulb. Our guide on how to replace a tail light walks through it.

After you fit it

• Check the fog light works, and the dashboard symbol comes on
• Look for gaps around the unit, and check that it sits flush
• Check the aim. Some front fog lights have an adjustment screw, and a badly aimed fog light can dazzle other drivers
• Check for moisture inside the unit over the next few days

If it still doesn’t work, our guide on rear fog light not working shows how to check the holder, fuse and wiring.

When to get a garage to do it

• You can’t reach the fixings without removing the bumper
• Your car has LED fog lights with control modules, sensors or a camera close by
• A fuse keeps blowing after you replace it
• You’re not comfortable working on the wiring

You can find a repair shop if you’d like a professional to do it.

Buying a used fog light

A matching used fog light is often the more affordable option. Before you buy, check the lens for cracks and moisture, and make sure the bulb holders, mounting tabs and plug are intact. Ask whether the surround or bezel is included, if you need it. You can browse used fog lights on Autolight and filter by make, model, year and side.

Once it’s fitted, it helps to know when to switch it on. Read when to use fog lights in Ireland.

Replacing a fog light FAQs

Can I replace just the bulb instead of the whole fog light?

If your fog light uses a bulb, usually yes. If it has built-in LEDs, you often need to replace the whole unit.

How do I know which bulb my fog light needs?

Check your owner’s manual, or look at the number or shape on the old bulb. Match the type exactly.

Do I need to replace both fog lights at the same time?

Not usually. You can replace just the one that’s faulty.

Can I fit a used fog light?

Yes, if it’s the correct unit for your car and it’s in good condition. Match the make, model, year, side and position, and check the plug and bulb holder.

Do fog lights need to be aimed?

Some do. If yours has an adjustment screw, check the aim after fitting so the light doesn’t dazzle other drivers.

Need a replacement unit?

Browse used car fog lights in Ireland and filter by make, model, year, side and county.