dbone996

Sorry, I know some may say the answer is already on this site but I could not find it. I seem to have trouble searching for anything within this site, the response is usually, "The following words are either very common, too long, or too short and were not included in your search". I have had more luck using google to find threads inside this site.

I’ve searched through the posts on his sight and elsewhere but have not found a solution to my headlight problem. I have found clues and some information to help rule out some areas but I’m still lost on what else to try. My headlights raise as they should but do not light. All other lights function perfectly. I was not able to find any diagrams for my exact year so I’m a little in the dark on how else to troubleshoot. I own a 79 928 auto and a 80 Petrol Blue manual car so I was able to borrow the headlight and ignition switch from the 80 to help rule areas out. I originally suspected the relay but my 1980 car has the different relay setup that is not transferable so I manually tested the 1979 relay, it appears to be good. I tested it by applying power across pins 85 and 86 when I do this the contacts close and I have continuity between pins 30 and 87. I also made sure the relay contacts were clean. I have no power at pin 30 on the relay and no power at any of the four headlight fuses. Today I inspected the panel where all the fuses and relays are located, its clean, not corroded and none of the wires contacts have pushed back in the panel that would keep the relay from making contact. I’m wondering if the problem is up front in the motor area. I’ve noticed the headlights don’t illuminate until the headlight are fully up so is there some sort of switch there that is denying power to the relay? I did clean the four connectors by the light motor but all looked good.

Can someone please explain how the headlight circuit functions or provide or direct me to to a diagram that would help me understand? I did find part of an 1980 diagram but my 79 is a little different with separate relays.
The manual shows the headlight relay is located the second from left, top row (IV).

When the ignition is switched on the relay closes this seems weird to me. I would think it would only close when the headlights are turned on and why are there not two relays, one more for high beam? I don’t really understand what’s going on here. I’ve have some electrical knowledge and no how to use a multimeter. Below is a list of what I have tried and found.

Relay appears to be good part #92861512700
Fuses are good
No power at any of the fours fuses
No power at headlights
Bulbs are good
Headlight switch is good
Ignition switch is good
Parking and fog lights are good
Headlights raise and lower when ignition is on.
No visible corrosion

Swapped ignition switch
Swapped headlights switch
checked grounds
Cleaned fuses
Cleaned the four connectors up at headlight motor
Tested and cleaned relay

928S MN

What about the high & low beam assembly in the turn signal housing? Is your problem with both high & low beams not lighting up?

Rusty928

I just began having a similar problem with my headlights on a US 86.5. The problem started with the headlights poping up and lowering but did not actually turn on while up. I just recalled while writing this that I didn't test the high beams, but all other lights worked. I started with the fuses and relays. Fuses looked good so I tried switching out the old relay and added the new one. Now I have the opposite problem. The headlights do not pop up or down but they turn on. If I put the old relay back in, raise the headlights, turn off the car, insert the new relay and start the car again I can now turn the headlights on and off while they are in the raised position; however, I cannot get them to go back down unless I replace the relay again. The plugs seem good in the fuse box. No major corrosion that is noticable. Any other ideas to troubleshoot the issue?

Thanks!

jpitman2

Do you not have any wiring diagrams for the 79? Are the 2 separate relays ordinary units that can have a spare (horn) swapped in to test? Assuming you have the same lift motor and 4 wires up front, I would suggest there is a failure in the copper wiping blades that sense when the lights are up - grease has dried and hardened, or some corrosion has prevented contact.
These 2 statements seem contradictory:-
My headlights raise as they should but do not light.
and
I’ve noticed the headlights don’t illuminate until the headlight are fully up
This last is the correct behaviour.

jp 83 Euro S AT 57k

skpyle

Hello dbone996, this may or may not be of help to you. Read post #92 in its entirety. It is my shenanigans with the headlight motor on the Red Witch:

https://rennlist.com/forums/928-foru...d-witch-7.html

Good Luck!

Alan

I know this was a long time ago, came across it searching for some other details this is relevant to. On a 77-79 the headlight relays are single cans - not the double socket width can multi-relays of the later types. There are 5 relays controlling headlight behavior:

A - Headlight Relay (XIII) Turns power on to the Headlight Dimmer Relay
B - Headlight 'Dimmer' Relay (XIV) Switches between High Beam and Low Beam
C - Headlight Control Relay (XVI) Controls switching Off the beams when the headlights are on but not yet rotated fully up
D - Concealing Headlight Relay (III) Drives the Pod Motor (rotates only in one direction but has 2 stopping points Park Up & Park Down)
E - Headlight Safety Relay (IV) Controls the Pod Motor stopping points: (Park Up & Park Down) using the motor limit switches (feeds C for HL on only in Park-Up)

So if your headlight pods don't rotate: suspect HL switch, motor fuse, motor, motor track/diodes or relay D/E. If they rotate up but don't park properly or keep going up/down: suspect the motor track/diodes or relay E. If they rotate up and park properly but don't illuminate suspect bulbs, fuses and relay B/C. If there is a problem switching between low & high beam or if one beam position doesn't work suspect fuses, bulbs, combo switch or relay A

Alan