gbarron

Last night I turned on my headlights (89 S4) and the buckets went up but the headlights didn't come on. All other lights came on as usual. I did some troubleshooting today and here is what I found.

I was able to manually get the lights to come on by taking the outer casing off the relay assembly, re-installing it on the panel, and physically pushing the contacts together when I have the headlight switch turned to position 2. At this point the contacts stay closed (lights stay on) until I turn the headlight switch back to position 1 where said contacts then release and the lights go out. Turning the switch back to position 2 again does nothing until I push the contacts back together again.

Here is where I got stumped. When I push the contacts together and they stay together is it the coil holding them or is it the current flowing through the contacts? In the factory schematic and the the schematic shown on the relay case this coil in question recieves its signal to energize from the printed circuit board (part of the relay assembly). I think either this circuit board is faulty or the coil is weak as it appears to be getting a signal from the headlight switch because the contacts release when I turn the switch back to position 1.

Before I rush out and buy a $100+ relay for the headlight system I want to be sure it is not a problem with the actual headlight switch. Has anyone run into this before? If so, how did you isolate the problem to the relay or switch?

For those of you good with electrical schematics here is a link to what I am looking at:

http://www.cannell.co.uk/928_Worksho...%20Diagram.pdf

I used the '87 schematic as it is easier to read than the '89 version posted. They are basically the same.

Looking at page 4 (my S4 is an ROW car) you can see the headlight system relay in the lower part of the schematic (desiganted XXIII XXIV). The contacts I am physically closing are connecting terminal 30 to terminals 56a or 56b (high/low beam ciruits). The printed circuit board is the piece shown to the right. As you can see this board controls the coil for these contacts.

Any and all help is greatly appreciated!

Glenn

Mrmerlin

try cleaning the contacts that are inside the relay, also check that the contact that turns on the headlights isnt too far away from its contact point, sometimes a lil bit of bending is necessary to keep the contacts close.
The relay coil is responsible for holding the contact in the closed position, irrespective of the fact the current flowing or not.
Chck carefully that the relay coil wire isnt broken near the base of the the PC board if its broken then the coil wont energise

gbarron

Thanks Merlin. I checked again and the contacts are good. I also looked at the clearance and it looked good too. I then tried physically closing the contacts with the headlight switch in position 0 or 1 and the lights would come on but the contacts would not stay closed when I released them.

I think this pretty much confirms that the coil is weak as in headlight switch position 2 they will stay closed when I push them together. It looks like the coil isn't strong enough to pull in the contacts but is strong enough to keep them together when I manually push them together.

Glenn

Alan

It isn't the switch.

Alan

Mrmerlin

the coil will only be energised with the key in the #2 position for the headlights to be ON now being up is another story.. If the contacts will stay closed when the key is in #2 then try bending the contact strip a bit closer if still no joy then the coil isnt work as it should so either one of the coil wires is broken or there are other problems with the relay

Tampa 928s

I found a shorted transistor in my relay along with a bad diode in the motor Assembly. Looking for a dead one to salvage parts from.