Rear Fog Light Question, When does it work?

[crazy like a fox]

This may be a silly question, but do the rear "fog lamps" come on with the brake lights, or just with the fog lamp switch? 1991 240 sedan

[Dippydog]

Rear fogs should only come on when switched on,not in conjunction with the brake lights.

[crazy like a fox]

THan ks. Likely some failure in the trailer wiring. Should be a relatively easy fix

[Stephen Edwin]

Originally Posted by crazy like a fox

THan ks. Likely some failure in the trailer wiring. Should be a relatively easy fix

You could be "very right" there. High intensity rear light issues are notorious when the vehicle has towing electrics.

Good luck and enjoy.



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[crazy like a fox]

I had no idea! Since I don't plan to do any towing with it, I think I'm just going to remove the trailer wiring.
Thanks for the information!

[crazy like a fox]

No luck. I suspect that there is no power on that side. No big issue though - I'll just splice in a wire to the side that works.....

[Clifford Pope]

Originally Posted by Dippydog

Rear fogs should only come on when switched on,not in conjunction with the brake lights.

They come on only when switched on, when the headlights are on, which requires the ignition to be on.

[loki_the_glt]

Originally Posted by Clifford Pope

They come on only when switched on, when the headlights are on, which requires the ignition to be on.

For early cars, i.e those with the big yellow switch mounted on "switch alley" the rear fog lights are wired in such a way that they'll come on with any lights -DRLs, side lights, dip or main beam. Fro later cars, where the fog lights switch is onthe instrument binnacle they're wired through the headlamp position.

[Stephen Edwin]

Originally Posted by crazy like a fox

No luck. I suspect that there is no power on that side. No big issue though - I'll just splice in a wire to the side that works.....

I had not understood. I think you are saying the high intensity rear lamp does not work at all on one side?

If that is right. Back to basics. Check bulb. Check contacts. Do check the earth. Trace the wiring with a test light.

Good luck and enjoy.


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[crazy like a fox]

I went back to basics. At least a crack in the circuit baord. and a break in the wire to the board. Did a workaround and got it fixed.
Thanks all for the information!