The fog light symbol on your dashboard tells you that your fog lights are switched on. The short answer: a lamp symbol with wavy lines through the beam means fog lights are active, a lamp pointing left usually means front fog lights and a lamp pointing right with a wavy line usually means a rear fog light. Use them only in fog, heavy rain, or falling snow when you cannot see far ahead, and switch them off when visibility improves, because bright fog lights in clear weather can dazzle other drivers.
Fog lights sit low on the car and throw a wide, flat beam close to the road. That low beam lights the road surface without reflecting as much glare back from fog as normal headlights do. This guide explains how to read the symbol, how front and rear fog lights differ, when to use them, and what to do when the symbol stays on or the lights do not work.
How to read the symbol
Look at the direction of the lamp in the symbol. Your action: if the lamp points to the left and the beam lines slope down, you are looking at the front fog light symbol. If the lamp points to the right and a single wavy line crosses the beam, you are looking at the rear fog light symbol. Some cars show the symbol in green for front fog lights and amber for a rear fog light, but colour alone is not a reliable rule, so check the direction of the lamp first.
Do not confuse a fog light symbol with a normal headlight symbol. Your action: a headlight symbol usually shows straight beam lines, while a fog light symbol shows beam lines cut by a wavy vertical line. If you are unsure, switch the fog light control off and watch whether the symbol disappears. That simple test confirms which control belongs to that symbol on your car.
Front fog lights and rear fog lights
Front fog lights help you see the road edge and lane markings in poor visibility. Your action: switch them on together with dipped headlights when fog, heavy rain, or snow makes it hard to see more than about 100 metres ahead. Keep your speed down and increase the gap to the car in front, because fog lights improve the view close to the car but do not let you see far ahead.
A rear fog light is a single bright red light at the back of the car. Your action: use it in thick fog or very heavy spray so traffic behind you can see you sooner. Switch it off as soon as visibility improves, because a rear fog light is brighter than a normal tail light and can be mistaken for a brake light in clear weather. If your car has a rear fog light, learn where its switch is before you need it in fog, not during a foggy drive.
When to use fog lights and when to switch them off
Use fog lights when visibility drops sharply and dipped headlights alone are not enough. Your action: in fog, switch on dipped headlights first, then add front fog lights if the road edge is still hard to see, and add the rear fog light if traffic behind you may struggle to see you. In light mist or drizzle, dipped headlights are usually enough, and fog lights add little.
Switch fog lights off when you leave the fog, enter a lit town, or join a queue of slow traffic in clear weather. Your action: make switching them off part of your routine when visibility improves, just as you would switch off main beam when another car approaches. Leaving a rear fog light on in clear weather is the most common fog light mistake, and it can confuse the driver behind you.
What to do when the symbol stays on
A fog light symbol that stays on usually means the switch is still on, not that the car has a fault. Your action: check the fog light switch and the headlight stalk, and switch the fog lights off. If the symbol goes out, the system is working normally. If the symbol stays on after you switch the control off, or the lights stay on with the switch off, book an electrical check, because a stuck switch or relay can drain the battery and dazzle other drivers.
If the symbol appears but no fog light works, check the bulbs and fuses first. Your action: look at both front fog lights and the rear fog light, and check the handbook for the fog light fuse location. One failed bulb usually means a bulb replacement, while both front lights failing together points more to a fuse, switch, or wiring fault. Do not drive in thick fog with no working fog lights if you can avoid the trip, and slow down and use dipped headlights if you must drive.
Lesson from everyday garage work
A common pattern in everyday garage work is that a driver arrives worried about a warning light, when the light is simply the fog light indicator. The lesson is to read the symbol before assuming a fault. Your action: learn the fog light symbols for your car in daylight, practise switching the front and rear lights on and off, and note which symbol belongs to each. That five minute check in the driveway saves worry on a foggy night.
For other dashboard warnings, read our guide on car dashboard symbols and meanings, check what a brake light on the dash means when a red warning appears, and read how to change a front light bulb if a front lamp needs replacement.
Frequently asked questions
Can I use fog lights in rain
Yes, when rain is heavy enough to cut visibility sharply. Your action: use dipped headlights first, add fog lights only if the road is still hard to read, and switch the rear fog light off when spray clears. In light rain, fog lights are not needed and can add glare.
Do fog lights replace headlights
No. Fog lights are an extra aid, not a replacement for headlights. Your action: always use dipped headlights with fog lights, because headlights light the road ahead and make your car visible from the front, while fog lights only add a low, wide beam close to the car.
Why does my car have only one rear fog light
Many cars fit a single rear fog light, usually on the driver side, because one bright red light is enough to warn traffic behind. Your action: do not assume the other side is faulty if only one rear fog light lights up. Check your handbook to confirm whether your model has one or two rear fog lights.
Is it illegal to leave fog lights on in clear weather
Rules vary by place, but using fog lights when visibility is good is widely treated as dazzling other drivers and can draw a fine in many areas. Your action: switch fog lights off as soon as visibility improves, and treat the rear fog light with extra care, because it is the brightest and most likely to confuse drivers behind you.
The fog light symbol simply shows that your fog lights are on. Learn which symbol is front and which is rear, use them only when visibility is poor, and switch them off when conditions clear, so you get the benefit in fog without dazzling anyone in clear weather.