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I’m almost all done with rehabbing my automatic 1986 928 S2 Euro 16v Twin Dizzy. Just a bit of applicable background, it was rat food and needed a lot of work, especially electrically. My immediate trouble now is that recently (after working fine for 9 months) my headlights will flip up but not turn on. All applicable fuses look good. I listened for the clicks of the dual relay and there was one for the motor to turn on and one for the lights to turn on. Wiggled the relay but still no luck. Fog lights and brights work fine. I disconnected the battery and pulled the relay. All looks fine. I read it could be the ignition switch and tried wiggling it with no luck. I took a drive for 30 minutes and the lights came on randomly after 20 minutes. After shutting off the car for about an hour and trying to fire them up again, back to original symptoms. Lights pop up but don’t turn on. Any help or advice is appreciated! I’ve read through this post, as well.
Have you checked/cleaned the four connectors that come out of the headlight motor unit, next to the radiator. Maybe the rats did just enough to make an intermittent connection, they’ve been known to have a sense of humor.
To me this sounds like a short in the wire to the regular beams since the high beams work and the problem comes and goes. I think I would double check to see if both headlights are out and not just one. then would follow the wires from the headlight bucket back to see if I could find the short. thinking about this some more It might also be a loose connection so checking the connections to the headlight switch and the ignition switch might find the issue too. It will be interesting to see what you find out.
So, I did recently have the car painted and they removed the headlight housing to spray them separately. I removed the housings and saw that the right lamp was not plugged in fully (pic below). I plugged it in fully and... no luck! I checked for power on the “drive” and “ground” contacts on both headlights with the lights on and there is no power to either.
This is a typical issue with our aging cars. In almost all cases, after the easy/obvious/blind tries don't work (did you throw a new relay at it yet?), the procedure is pretty much always the same: Dig out the ohm/voltmeter, dig out the electrical diagrams for your car, and start sleuthing. And as is usually the case, you'll probably want to start at the central electrical panel where you can determine what's happening both with the input to the relay in question (for instance, is the expected voltage arriving at the appropriate relay pin(s) when the headlight switch is turned on?) and on the output of the relay in question (is the expected voltage going out on the correct output pin(s), and how about at the appropriate pin(s) in the appropriate connector at the lower edge of the central panel)? Is the fuse ok? Are the pins all clean? Is there any melted wiring or disconnected pins?
You can also do some continuity checking with the ohm setting on your multimeter to see if the pins going out to the headlights (from the relay pins and from the connector pins at the lower edge of the panel) are continuous to the connections at the headlights themselves. Those buckets swinging up and down over the years, coupled with old, original and crispy wiring harnesses, can certainly cause the wires to break and/or insulation to break and cause a short. You should also test continuity from the appropriate "input" pins up to the headlight switch or wherever else the wiring diagrams lead you.
You can probably also do some sleuthing at the headlight switch itself if necessary.
And while you're at all that, take the time to clean up all the pins/connectors/electrical metal-to-metal contacts that you work with. I believe a small brass brush has been recommended. Have your can of DeOxit at the ready. It might not be a bad idea to remove your CE panel and give it a good once-over, including removing all the relays/fuses/connectors, cleaning, DeoXiting, placing them back, and reinstalling (if you haven't done that recently).
I'm not familiar in great detail with the headlight circuit so can't tell you exact pin numbers and so forth. But, here's another thread I put together if you're not familiar with the electrical diagrams that should be very applicable to your '86 where you can figure out everything: https://rennlist.com/forums/928-foru...r-dummies.html
Have you checked/cleaned the four connectors that come out of the headlight motor unit, next to the radiator. Maybe the rats did just enough to make an intermittent connection, they’ve been known to have a sense of humor.
Thanks, gazfish! I can see the connector but can’t quite get to it as it’s on the wrong side of the headlight motor. Do I have to remove the headlight motor to get to the plug? Seems like it. If so, might take that apart and clean it up, as well.
To me this sounds like a short in the wire to the regular beams since the high beams work and the problem comes and goes. I think I would double check to see if both headlights are out and not just one. then would follow the wires from the headlight bucket back to see if I could find the short. thinking about this some more It might also be a loose connection so checking the connections to the headlight switch and the ignition switch might find the issue too. It will be interesting to see what you find out.
Thanks, Dark Shark! Both headlights were working fine a few days ago and both went out at the same time. I assume both the headlight switch and the ignition switch require pod removal to check connections?
This is a typical issue with our aging cars. In almost all cases, after the easy/obvious/blind tries don't work (did you throw a new relay at it yet?), the procedure is pretty much always the same: Dig out the ohm/voltmeter, dig out the electrical diagrams for your car, and start sleuthing. And as is usually the case, you'll probably want to start at the central electrical panel where you can determine what's happening both with the input to the relay in question (for instance, is the expected voltage arriving at the appropriate relay pin(s) when the headlight switch is turned on?) and on the output of the relay in question (is the expected voltage going out on the correct output pin(s), and how about at the appropriate pin(s) in the appropriate connector at the lower edge of the central panel)? Is the fuse ok? Are the pins all clean? Is there any melted wiring or disconnected pins?
You can also do some continuity checking with the ohm setting on your multimeter to see if the pins going out to the headlights (from the relay pins and from the connector pins at the lower edge of the panel) are continuous to the connections at the headlights themselves. Those buckets swinging up and down over the years, coupled with old, original and crispy wiring harnesses, can certainly cause the wires to break and/or insulation to break and cause a short. You should also test continuity from the appropriate "input" pins up to the headlight switch or wherever else the wiring diagrams lead you.
You can probably also do some sleuthing at the headlight switch itself if necessary.
And while you're at all that, take the time to clean up all the pins/connectors/electrical metal-to-metal contacts that you work with. I believe a small brass brush has been recommended. Have your can of DeOxit at the ready. It might not be a bad idea to remove your CE panel and give it a good once-over, including removing all the relays/fuses/connectors, cleaning, DeoXiting, placing them back, and reinstalling (if you haven't done that recently).
I'm not familiar in great detail with the headlight circuit so can't tell you exact pin numbers and so forth. But, here's another thread I put together if you're not familiar with the electrical diagrams that should be very applicable to your '86 where you can figure out everything: https://rennlist.com/forums/928-foru...r-dummies.html
Thanks rjtw! I’m familiar with the wiring diagrams at this stage. I may try to pull the headlight relay and test PIN 15 and/or 30 (15 is hot with ig switch on RUN, 30 is always hot), in hopes they have 12 volts. If not, that would answer why I don’t have power at the lamps. From other reading, it could be the female connectors for the headlight relay behind the CE panel, as well.
Do the fog lamps work ?
have you taken the relay cover off to clean the contacts inside it?
The first picture I posted has all three of the light switches turned on (main, fog/parking, brights). As you can see, the fog (outer/lower) and brights (inner/lower) are on but the main driving lights are not. I haven’t pulled the relay cover off yet. Can try cleaning the inner contacts and solder any damage tomorrow.
12-12-2020, 03:33 PM
Solved: Headlight Issue
I checked for power on the “drive” and “ground” contacts on both headlights with the lights on and there is no power to either.
