1997 Audi A6 C5 (Type 4B) Fog lights inop

[if11677]

Hi there. I have an 1997 Audi A6 C5 (Type 4B) 2.4i V6 (AGA). My front and rear foglamps have stopped working and the bulbs and fuses seem ok. Is it common for the switch pack to be faulty. It is the type were you pull the headlight switch out once for front fogs and twice for rear. The switch itself lights up ok exept the fogs tell tale ones and all other lights work ok.

[yaman]

Have a look at the fog-light relay first. Should be 381

Regards
Jim

[Peter D]

Check fuse 36. There is no relay, the lights are wired dirctly to the switch. Regards Peter

[yaman]

There is no relay,

Pray tell me then, what purpose doth the purple relay 381 hath?

Regards
Jim

[Peter D]

Hi Jim, I checked on a 4F C5 diagram and there is no relay in the electrical circuit. However there is mention of a Fog lamp relay in position 6 of the 13 point relay carrier behind the drivers site shelf. It also suggests that it is the fuel relay on the TDI.

The wire from the switch is 1.5mm as it has to power two front fogs and the wire for the rear fog is 1mm as it only powers one rear light.

Not even the headlighs on this model has a relay in the circuit.

Perhaps the older chassis A100 had a relay.

Regards Peter

[yaman]

Think the front-fogs need a relay in the circuit on account of
them getting auto-switched off when the main beam is switched on,
without the driver touching the main lighting switch, and visa-versa
when its dipped.

Regards
Jim

[Peter D]

But they do not get switched off other than by the light switch itself or the ignition being turned off. Regards Peter

[skyegtb]

Hello, I found this old thread when searching for help with a similar problem. My car is a 2002 allroad C5 2.5tdi

Problem: Rear foglight will not illuminate. Only 4V measured at rear foglight bulb connector when switch is activated.

The bulb and bulb holder for the rear fog are good.

I have checked all the wiring inside the bootlid and all seems fine. There is continuity to earth from one of the wires at the connector, but only 4V at the other.

I have a towbar on this car and wonder if the connector there is damaged thereby making the car think it has a trailer attached and killing the fog-light. I plan to investigate this tomorrow.

Any suggestions of what else to check? Is it likely the switch on the dash is defective? Any tips on how to test the switch?

[niall campbell]

I would trace the wiring back from the electric socket of the tow bar to the fog lamp, it might be connected with a scotch clip and its badly damaged the wire

if the towbar electrics go into a box and then tap into the car electrics, then possibly the box is broken ............................................. OR the electric connection for the towbar is badly corroded and shorting out the wires ?

That might fool the car into believing a trailer is fitted and dimming the foglamp, but I don't think it dims the fog light; I thought it switched it off ??

[skyegtb]

Thanks, that will be the next thing to check. Just for info I quickly pulled the switch out from the dash and tested it. The grey/white wire there connects to the bulb socket in the tailgate but at the switch it gives 12V yet at the socket 4V. I checked the earth in the tailgate and it is good. So, it looks like the switch is good, the earth is good, so the only things left to cjheck are the suggestions above and finally the grey/white wire. The wire checking will be a real pain though as it appears to go under the roof lining after exiting the boot area.

I'll update this thread tomorrow after more investigation. I'm hoping it turns out to be something simple related to the towbar electrics.