weirdscience

I finally got some room in the shop so I decided to tackle some on going issues. We started with the headlights, they pop up but dont turn on. We searched the Rennlist archives and found some good info but no solution. Ive got the factory wiring diagram so we checked all the wiring, tested the switch, relays and ground theres correct voltage where needed and all the grounds are good. When we jump power to the headlight fuse they come on. Were going to check behind the fuse panel as the last resort. I had some electrical work done by a respectable shop and they had to go into the fuse panel so maybe a wire got pulled or cut somewhere. Any Ideas or advise would be appreciated. Thanks.

Steve Tacheny

I just had the same problem on my car in July. Turned out to be the headlight relay. Hope this helps

Steve

Alan

Test the headlight switch output at B5 on the CE panel. It should be active with the headlight switch in headlight position and ignition in accessory or ignition.

Test the voltage levels on N6, N7 & N8 with ignition on, lights on headlights (pods up) and with ignition on and all lights off (pods down) - Report what you have ?

It is most likely that the headlight relay is faulty (stuck contacts)

Alan

tailpipe

ok this will sound dumb but make sure the light bulbs are actually plugged in at the headlight my 79 euro that i rescued had nice new lights that didn't work also took some messing around till i actually looked to see they werent plugged in lol did i feel dumb but then relized that the plugs didn't fit the lights i had to file down the tangs on the lights to fit the spade clips inside the plugs i'm not sure if they were ment for the H4 but they didn't want to fit the regular sealed beams i did finally replace them with some cibies much better good luck


paul with 4 79 928s

Mike Frye

He said when he uses a jumper at the fuse, the lights come on.

I try never to respond if it's an electrical problem and Alan has already checked in.

Steve Tacheny

Perhaps I should explain what happened to mine. There is 3 relays inside the HL relay. 1st on picks up when you turn on switch. 2nd on picks up and raises headlights. When they raise and contacts make up in motor 3rd one picks up and turns lights on. I took mine apart and tested it inside and found the 3rd winding that pulls the contacts in for headlights to turn on was burned out. Hope this helps


Steve

Alan

Not quite and it varies with year...

One contact set controls driving the pod motor - on a pre-S4 the headlight motor runs only one way and stops in 2 positions: up & down. The second contact set controls the turning on of the headlight beams - it is disabled whenever the headlight motor is still running. The third contact set controls the switching between high & low beam.

On S4+ models there are 4 relays - an extra one for the headlight pod motor which now runs in one direction for up and reverses direction to go down. The other switching is essentially the same. Relays & motors are not at all compatible between the Pre-S4 & S4+ models.

The relay coils rarely burn out - but the contacts often get stuck (~welded) open/closed or get so much oxidation they no longer make good contact. Usually the best solution is HL relay replacement - though expensive! Temporary repairs can be attempted (nothing to loose) - but usually are not a good long term solution.

Alan

Steve Tacheny

Mine was just like I described. No light on high or low beam but if I pushed the 3rd set of contacts together with my finger I had both high and low beams so it was the 3rd set and they were open, not stuck shut. Tested the coil to pull them shut with an ohmmeter and it was open, hence, burned out. I unsoldered the bad coil and points from the relay, soldered in some jumper wires and hooked up a relay to test and low and behold I had BOTH high and low beams.

Steve

Steve

Alan

I'm not saying a coil on yours didn't burn out... but this is quite rare - (mainly because they operate at very low power).

Primarily correcting what you said on operation... the headlights are confusing enough already that we need to keep the story straight...

Alan

steeveeo

Thanks for the help guys, It turns out there was a bad connection on the relay socket on terminal 56 so the headlight relay wasn't getting the signal to switch on. Thanks again for the help.

Steve Bull
BSM Exhaust Works

Steve Tacheny

No problem at all. Your right, that headlight circuit is a bugger to understand. Just wanted the OP to know that it is a possibility

Steve

Steve Tacheny

Oops! I'm too slow at posting I guess. Glad you got it fixed

Steve

weirdscience

Thanks for all the input guys...

weirdscience

now its on to the power door locks.

Rod Handsfield

Tonite the headlights quit working on my '88. The interior lights were still on after closing the door. When I switched on the headlights, they came up: the interior lights failed and immediately came back on
but no headlights. Driving lights work fine when high beam switch is activated. Where do I start?