Late E30 ('92) Fog Light Troubleshooting

[JimmyP]

Hi guys,
I am troubleshooting non-working factory fog lights on my '92 MTech Cab.

Here is where I am with it, maybe there is some well known failure point that someone can share before I start ripping the dash apart.

1) The fog lights do work when jumped 12v direct to their fuses.

2) Fog Light Relay has 12v to pin 30 and Pin 86, Ground to pin 87 with Key ON, Headlights ON.

3) I think the problem is continuity from Fog Light Relay socket for pin 85 to Fog Light Switch, which is the Grey wire that runs through C103 on pin 14.

Under no circumstances power on, lights on, lights off can I establish continuity from Fog Light switch grey wire to socket 85 on fog light relay.

The Blue / Grey wire on the other side does establish continuity to Ground as its supposed to.

My theory is somewhere there is an air gap in that grey wire between the fog light switch and pin 85 on the Fog Light Relay, and in-between those two devices is C103.

Wondering:
• If anyone has run into this before?

• If my diagnosis sounds correct?

• If there is any known failure mode of that grey wire between Fog Light Switch and pin 85 of the relay?

Full disclosure, this car's lighting was heavily modified when I got it.
It had some kind of HIDs in the low beams and fogs, City Lights, it was jumpered all over to make all 6 lights operate at one time.

I have stripped all that away and returned everything to stock components operating on stock wiring.
I now have all lighting working exactly as BMW intended but the fog lights.
I "think" I am almost there if I can establish continuity from switch to Pin 85 (or at least thats how I am reading the ETK and all the posts I have searched through on here).
I just cannot find via searching this exact problem.

Any thoughts or help appreciated.

[tim88325is]

I just fixed my car that had one side out.

The wire just outside the fog lamp's factory connection failed, I cut off the connector and crimped on a new generic female connector that happened to fit.

I have found that wiring and connectors fail much more than switches or other components. I would make sure you have continuity through the harness from the fog lamp location back upstream to the first available junction.

My experience is the wiring harness that feeds the front of the car receives a lot of heat, vibration, and exposure that degrades the insulation causing shorts at seemingly illogical locations.

[JimmyP]

I just fixed my car that had one side out.

The wire just outside the fog lamp's factory connection failed, I cut off the connector and crimped on a new generic female connector that happened to fit.

I have found that wiring and connectors fail much more than switches or other components. I would make sure you have continuity through the harness from the fog lamp location back upstream to the first available junction.

My experience is the wiring harness that feeds the front of the car receives a lot of heat, vibration, and exposure that degrades the insulation causing shorts at seemingly illogical locations.

Thanks.
The output side is now fully working after I resored it to stock components.
If I jump pin 30 of the fog light relay (or any 12v source) to the output pin of Fuse 29 and 30 I can make both fog lights come on.

I believe where mine is failing is on the control side of the relay.
The only thing that doesn't seem to be working is continuity to ground from socket 85 which passes through the fog light switch.
The switch tests good and I have ground on the blue / grey side of the wiring.

[JimmyP]

I am bumping this thread because of C19 I have finally had time to clean up a bunch of other wiring issues on my Cabrio and my FINAL hurdle is to get the foglights working to have (what I believe) is a 100% working car).
This car has had some very poor (and questionable) wiring work done on it previously, all of which I have now fixed properly except the foglights.

If you read the initial post the foglights work. I have power to Pin 30 of the relay and via jumper to pin 87 the foglights come on.
The problem is on the relay's control side.

When I traced the foglight control wire to the fuse box, Pin 2 of the fog light switch (GREY) should go to pin 85 of the fog light relay. I did NOT have continuity from the foglight switch pin 2 to foglight relay pin 85.

I opened the fuse box, what I found inside the fuse box was someone had scotchlocked the grey fog light control wire that was supposed to go to pin 85 and provide ground, instead it was connected to pin 86 of the fog light relay and CUT the wire that fed pin 86 previously. Pin 86 should have provided relay control side 12v. With the scotchlock removed it is now just dangling there as a dead lead out of the circuit board.

I DO have continuity on the grey wire all the way to the fog light switch, and the fog light switch works (which in a normal situation provides the ground for the fog light relay via pin 85).

QUESTION: Can anyone think of a way to work around this without de-pinning the entire fusebox?
I would love for the foglights to work, well as a matter of principal, they do work, I just cannot control them via the foglight switch.
There is not enough slack in the fusebox for me to get a good look at the underside or even work on it to see what has happened underside of the fog light relay pin 86 (except seeing the cut lead on pin 85).
I dont want to do anything crazy because right now I finally have the car at (almost) 100% except for the foglights but if anyone can think of a simple jump, work around (like how we jump relays to get Hi and Low beams to stay on together) to get control back to pins 85-86 of the relay I am all ears.
I do have a working run into the fusebox from the foglight switch that can provide control ground its just not attached to anything now, and currently no control 12v on the pin 86 side of the relay.

Thanks for reading this far!
Cheers
Jimmy P