I have a 1994 940
Occasionally when the headlights were on, the left turn, fog light and high beam indicator lights would be on but dim. Recently this happened at night and the dash lights were not working. (I did not have them turned off) I replaced the headlight relay. Did not fix the problem.
Here is what works and does not work.
When the parking lights are on all lights work except the dash lights and the indicator lights are on but dim.
When the headlights are on all lights work except the tail lights and the dash lights, the indicator lights are off.
When the fog lights are on (headlights on) all the lights work except the tail lights and dash lights, the indicator light for fog lights is on properly.
The fuses in the center console are all good.
What do you suggest I try next? A headlight switch?

 

I would check the bulb failure relay.

 

Replaced the bulb failure sensor-did not fix the problem.
Cleaned the ground on the left front near headlights, right side looked good. Are there any other grounds I should check.
Will change fuses and lights. Would you use a wire brush on the fuse panel? Any other suggestions? Know where I can get a wiring diagram that includes the fog lights?
Thanks

 

Did you clean the grounds good for the taillights?
Also make sure the sockets for the bulbs are ok.
This is the best I can do for a wiring diagram if I made it bigger than it would be about 4 to 5 pages.

 

The problem may be more general than just the lights... like a bad battery or alternator. You can do simple tests to other electrical components... next time you are stopped and idling, press the brakes, and listen for a change in the idle or see if your lights dim. If this occurs, the onset of your brake lights take away from what little power your car is generating. And this indicates an alternator problem or lack of battery charge.