960 rear fog light

[krismorgan]

Hi there,
My 1994 960 estate failed its mot on the rear foglight not working.I never even noticed it doh.
Anyway checked the bulb-fine,fuse fine,the fog switch was not even plugged in so done that-still nothing.So im thinking relay as i have no relay sound when switching it on.Can anybody tell me which relay i should be checking before i just wire an aftermarket one in?cheers.

[Stephen Edwin]

I can't answer re the relay. But.

Does your car have towing electrics? If so there are two other possibles causes to consider for the problem.

1. Many towing electrics sockets have a mechanical switch to switch the car high intensity rear lights orf when towing electrics are plugged in. Usually a simple piece of brass that makes and breaks the contact to the car's high intensity rear lights. That switch can fail.

2. There is apparently a possible failure in the "inner workings" of newer type towing electrics. I've seen it mentioned but I have older type towing electrics so I didn't pay much attention.

Good luck.

[krismorgan]

Cheers,never thought of that as it has extra wiring in the rear panel and i think it once had a tow bar before ownership.

[Laird Scooby]

The rear fogs don't have a relay. Check out Pg45 of this pdf :

http://www.myvolvolibrary.info/Tech_...Y94_Wiring.pdf

Do your front fogs work? Have you changed the bulbs in the rear ones? Does the warning light come on when you switch the rear fogs on? They only work on dipped beam by the way! Depending on your switch, you may have to switch the front fogs on first and then the rears (3 position switch) or if you have 2 separate switches, the front fogs will work on sidelights with ignition and if the front fogs are on, the rears should work as well.

Stephens idea of the towing socket could be worth a look - if you have a trailerboard with a fog light, plug that in and you should see if the rear fog works on that. If so then it's the disconnect circuitry at fault.

Also worth checking the bulb holders, sometimes the contacts can get dirty as well.

[krismorgan]

Cheers for that too.In the end there was no power to the fog lamp so i ran a wire with a new switch and all was fine,mot passed today,thanks for the ideas.

[Stephen Edwin]

That's good that you have the rear high intensity lights again, and a new MOT.

If the cause niggles with you, then the extra wiring must be suspect. And if it is towing wiring, that is a known cause of there being no power at the vehicle high intensity rear lights.

[Laird Scooby]

Originally Posted by Stephen Edwin

If the cause niggles with you, then the extra wiring must be suspect. And if it is towing wiring, that is a known cause of there being no power at the vehicle high intensity rear lights.

It should niggle - unresolved wiring problems can lead to fires!

[jonnyf90]

Originally Posted by Laird Scooby

The rear fogs don't have a relay. Check out Pg45 of this pdf :

http://www.myvolvolibrary.info/Tech_...Y94_Wiring.pdf

Do your front fogs work? Have you changed the bulbs in the rear ones? Does the warning light come on when you switch the rear fogs on? They only work on dipped beam by the way! Depending on your switch, you may have to switch the front fogs on first and then the rears (3 position switch) or if you have 2 separate switches, the front fogs will work on sidelights with ignition and if the front fogs are on, the rears should work as well.

Stephens idea of the towing socket could be worth a look - if you have a trailerboard with a fog light, plug that in and you should see if the rear fog works on that. If so then it's the disconnect circuitry at fault.

Also worth checking the bulb holders, sometimes the contacts can get dirty as well.

Fogs work with just side lights on.
In fact it’s illegal to drive in Sweden with dipped beam AND fogs. It’s one or the other

Cheers

[Stephen Edwin]

Originally Posted by jonnyf90

Fogs work with just side lights on.
In fact it’s illegal to drive in Sweden with dipped beam AND fogs. It’s one or the other

Cheers

Are you saying that in Sweden if one needs high intensity rear lights, one is only allowed to have "side" lights switched on at the front? I don't understand that.

In UK it is so far as I know usual that high intensity rear lights are wired not to work unless front headlights, or front foglights, are switched on. I think that is logical because if headlamps/foglamps are not justified how likely is it that high intensity rear lights can be justified?

Whether the high intensity rear will work with main beam as well as dipped is a moot point. On my 240 the high intesnity rear work with either headlamp dipped or main beam. After all one would not want the bright rear lamps going off if one flashes the main beam for example.

[jonnyf90]

The “high intensity rear lights” is unnecessary - they’re fog lights 🤣

It appears so. If the fog is as thick enough as to not be able to see where you’re going without dipped headlights, you should drive slower - which I think is their thinking.
“Proper” front fog lights have steeply angled beams allowing the driver to see the road and be seen easier without dazzling.

On my 960, the front fogs work with lights set to 0, Park or Dipped. The rear fogs only come on with dipped headlights

Cheers