Passenger rear light not working

[rjkoop]

The passenger rear driving light stopped working on my '81. The bulb is fine because I exchanged it with the driver's side rear and the bulb works fine in the drivers side. What's the best way to figure this out? I find it difficult to know (even looking at the wiring diagram) if the power isn't getting from the driver's light unit to the passenger side unit or if the problem exists in the passenger side light unit. What 2 connector pins worked the passenger side rear light? All other lights work fine. Weird.

[RRoller123]

The connectors can work loose, there are grounds nearby that get corroded, and the bulb socket itself is frequently corroded. The socket holder can get loose too over the years. So many possibilities. Trying working back from the socket with a voltmeter and see how far the power is reaching before there is a problem?

[rjkoop]

The connectors can work loose, there are grounds nearby that get corroded, and the bulb socket itself is frequently corroded. The socket holder can get loose too over the years. So many possibilities. Trying working back from the socket with a voltmeter and see how far the power is reaching before there is a problem?

Yep. I find it difficult to exactly determine the path of the + and - based on the wiring diagram. I hope it just takes patience. Logically if the drivers side is working 100% I should be able to determine the + and - for the driving light, trace it to the wires on the drivers side, determine the same wires on the passenger side and determine if I have power. If I'm getting + and - power to the passenger side for that pin then it must be a problem on the passenger side. I must be getting a good ground through the wire from the drivers to the passenger side light because all other lights work on the passenger side. And from what I can see the - comes from the wire on the drivers side body, through the drivers light board and then over a pin to the passenger side, correct?

I'll try again tonight.

Richard

[RRoller123]

Could be a broken or corroded trace on the PCB too, should probably check that as well. The entire rear lighting system was designed with a ridiculous level of complexity for the time.

[4uall]

older model however, this may offer some visual references

https://www.youtube.com/watch?v=kAIohDEEEGM

https://www.youtube.com/watch?v=EgwR9sYN5f0

[rjkoop]

Could be a broken or corroded trace on the PCB too, should probably check that as well. The entire rear lighting system was designed with a ridiculous level of complexity for the time.

Yep. I found that too. When I originally restored the car I had a few traces that I had to fix with some solder to make the connection. I'll check those too.

[rjkoop]

older model however, this may offer some visual references

https://www.youtube.com/watch?v=kAIohDEEEGM

https://www.youtube.com/watch?v=EgwR9sYN5f0

Thanks Jay. I'll check out those videos as well.

Richard

[spider2081]

To be sure I understand your question. are we talking about the light that lights with the headlight on/off switch in the middle position? If so As others mentioned the power for those lights passes through the drivers side light assemble. On the passenger side does the small square light in the side of the fender light? if it does the problem most likely is on the bulb socket on the passenger side PC board. The power from the driver side enters the passenger side then exits the 2 pin connector for the side lights. The marker plate lights also pass through the drivers side PC board it is fairly common for the plastic cover to be missing on these lights making it possible for them to short. If one of them does short, the drivers PC board could have been damaged. Do your Marker plate lights work??

[rjkoop]

To be sure I understand your question. are we talking about the light that lights with the headlight on/off switch in the middle position? If so As others mentioned the power for those lights passes through the drivers side light assemble. On the passenger side does the small square light in the side of the fender light? if it does the problem most likely is on the bulb socket on the passenger side PC board. The power from the driver side enters the passenger side then exits the 2 pin connector for the side lights. The marker plate lights also pass through the drivers side PC board it is fairly common for the plastic cover to be missing on these lights making it possible for them to short. If one of them does short, the drivers PC board could have been damaged. Do your Marker plate lights work??

I'm talking about the light that comes on when I switch on the headlights.

I'll check everything tonight and let you know.

[NSFIAT]

I had that *exact* same problem with mine - in the end it was a small break in the PCB. I hadn't caught it at first and was trying to chase demons elsewhere (grounds, wiring, bulbs, switches, etc).

[rjkoop]

I had that *exact* same problem with mine - in the end it was a small break in the PCB. I hadn't caught it at first and was trying to chase demons elsewhere (grounds, wiring, bulbs, switches, etc).

That's what I'm figuring as well. Just curious... was it the PCB on the driver's side or on the passenger side?

[NSFIAT]

I had that *exact* same problem with mine - in the end it was a small break in the PCB. I hadn't caught it at first and was trying to chase demons elsewhere (grounds, wiring, bulbs, switches, etc).

That's what I'm figuring as well. Just curious... was it the PCB on the driver's side or on the passenger side?

The break was in the driver's side board, which in turn was affecting the passenger side board. I would only have running lights / brake lights if the headlights were off. I suppose that's OK for daytime driving, but I'd rather be fully lit up!

The break itself was tiny and I missed it every time I came back to the PCB. It wasn't picked up until I starting testing with a meter . .

[rjkoop]

Took a closer look tonight and finally figured it out. Turns out that although all the fuses were fine, one of them must have not been making contact. I essentially took the fuses out, reinserted them and now everything works!

So if your passenger side rear driving light and the license plate lights aren't working it's 99% chance an issue with a fuse.

Thanks for everyone's help. Live and learn...

[spider2081]

For future reference, Fuse "H" an 8 amp fuse powers the Right hand rear side light, right side tail light and right side license plate light. It also powers the dash lights, the lights on indicator in the speedometer and the cigar lighter light. Fuse "A" is closest fuse to the steering column. So Fuse H is the 8th fuse from the steering column.

[DUCeditor]

I am so thankful for these and related posts.

The "blinkers" in my `77 had stopped working. Then, with daily use had become intermittent. Sometimes they worked, other times not. Grrr.

I'd cleaned all the contacts last season and would heve been surprised if that had been the issue -- especially since right and left were equally effected/uneffected.

Then the comments about the fuses came up. Not needing to be "blown," but simple not making good contact. So I went under the dash and rotated each in its mount a couple of times.

Now everything is working just fine. Such a simple "fix" - but one I only was made aware of considering here. So, again... THANKS!

-don