Hold On

UPDATED: REPAIRED> Driving home last night I get the Tail Lite Out warning at dash. When I get home I look and the right tail lite and side marker are out. OK the system works.
Today I go to fix it and start at the bulb. Bulb looks good,but I switch out anyway.Nothing. Get out my test lite. No power at the socket. Ck fuse Fuse good, power at both ends.

Open up hatch and ck power at light plug behind quarter panel. No power at the plug coming out of the harness. Now I have power at the main fuse panel but none at the plug at back.

I do a search...lots of stuff on this topic..
Questions:
1. Could the bulb check module be bad and keeping 12V from reaching the back plug?
2. Can this unit be opened for inspection for burnt components?
3. Can the check module be bypassed and does anyone have a wire diagram on how to bypass?

Mrmerlin

your problem in order of highest probability
1 bad ground connection,
2 bad power connection
3 corroded side marker light housing
4 mismatched bulbs
5 failed rear light socket
Stay away from the bulb controller

Rick3452

This just happened to me.... It was the little brown ground wire that ia attached to the rear wiper motor behind the tool panel, it was loose......bet thats it!
Best of luck...Rick

Hold On

Thanks for the advice. I went out this morning and cleaned all the grounds at the back of car. Nothing. All the bulbs are the same and good. removed and checked side marker assy. All good. All the lights at the back work except the pass. side running light and side marker. These two lights come off the same circuit and fuse. My problem appears to be no 12V at the one wire (grey/red) that feeds those lights at the inside plug at rear. That is what is leading me to think its the bulb controller. Any other suggestions appreciated.

Landseer

Sounds like you've narrowed it down.

What year is this car, BTW?

The ground for the fixture is behind the quarter panel, but I think you know that or wouldn't have gotten this far.

You can make power checks at the controller. Not sure why Stan says to say away from it, though. Maybe he has experience with them failing during troubleshooting?

Taillight/markers are fused side to side, but you know that. Two inputs to the bulb controller and two outputs.

Alan

As already mentioned by Stan - put the bulb controller at the very end of your list.. don't start there - its very unlikely.

How are you testing for power...? make sure your ground reference point isn't the bulb socket - connect it instead to the chassis - then what?

Alan

Hold On

Check everything again. Ran a jumper wire from output side of fuse #29 in main panel to pin on plug at back that feeds these lights. Bingo, lights work. Problem appears to be between main fuse box and main plug at back. specifically grey /red feed wire.

What components are between these two points or is it just wire harness?

I also removed bulb check unit. Opened it up, no obvious burnt components, cleaned all pins reassembled. made no difference. At this point, Im eliminating, bulbs,sockets, housing,fuse, grounds at back as possible reasons.

sorry forgot to mention car is a 1983

Landseer

Check power in and out of the bulb control unit to determine if the fault is in the distribution before the unit or after it, or the unit itself.

Left: S1 goes into bulb unit at terminal 7, out at terminal 4

Right: S2 goes into bulb unit at terminal 5, out at terminal 3

Hold On

Thats what I was just looking at on wire diagram. Off we go again..


Ok jumpered 12v input (pin5) to output (pin3) on bulb controller multi pin plug. LIGHTS WORK. It appears issue is within bulb controller between input and output to lights. Time to get out multimeter, open up unit and check things out.

Landseer

83 box is the last with mechanical reed switches.
84 box has electronic circuits and can be directly retrofitted into 83.
Not sure how far forward you can reach into the model years to find a replacement, but I think at least through 86 is identical.
There is a factory bridge plug, maybe a supplier could find one.
Or several of us have bypassed the units with our own rigged-up version.

Hold On

Light repaired. After I opened bulb controller, I cleaned a little crud off circuit board with some electronic cleaner and a soft toothbrush. resoldered a couple cracked joints. Did the same on the female side of the connector and reinstalled. Everything works fine (until the next 928 electrical gremlin strikes!!!) Thanks everyone who responded for the help.

Landseer

Nice fix.

Mrmerlin

glad you got it figured out , bulb controllers rarely fail , i wonder if yours got wet

Manfred

Nice work.