Porsche Repair: 85 944 Fog Light Issue, fog light, troubleshooting expertise

Question
Hi Dave,

I've got an '85 944 that is experiencing a little bit of trouble with the left fog light.  I thought it may have been the bulb, but after popping it out, I noticed that the filament was intact.  The connections on the front side and back under the car (through the rubber seal at the back of the housing) seem to be intact and properly connected.  The fuse is fine, as the right fog light is operating properly.

Are there issues that I'm just missing that could cause this sort of outage?

I did notice that one of the pieces that the mounting screws screw into is broken - it fell out when I removed the housing the first time.  It doesn't seem that it would be a problem (or a grounding issue), but who knows...

My troubleshooting expertise seems to be at its limits, any thoughts you have would be appreciated.

---
Darren Lloyd

Answer
Hi Darren,

I've looked at the wiring diagram and if the right light is working fine, then there really are only a few possibilities with the left light.  As both lights are controlled by the same relay and the same fuse your problem has to be either:

1.  The brown grounding wire is not really grounding anymore.  Check to make sure it is attached to a clean metal surface.
2.  The red/white power wire is broken or not attached to the light assembly anymore.  Get an inexpensive 12v tester and turn on the lights.  Test to see if the wire is carrying 12v to your test position at the light.
3.  The bulb looks OK but isn't.
4.  The electrical connections inside the light are faulty,

Let me know what you find.

Dave