1978 280z: Tail Lights, Dash Lights, and Side Markers not coming on/not working

[dylonwalk]

Hello!

I have a 1978 280z. My tail lights, dash lights, and side markers not coming on, on both sides. Headlights work.

1. I've replaced the stop light fuse with tail light fuse and the stop lights still worked. So that makes me think it's definitely not a fuse.

2. The stop lights still work even after changing fuse so that makes me think it's also not a grounding issue.

3. I've checked the continuity and voltage between the GW and GL plugs under the combination switch and got a signal (see attached photo for location) but no voltage

4. I checked the  continuity and voltage at the tail light sockets and tail fuse and got a single but no voltage going to them.

At this point I'm not sure what to do next. Any help would be appreciated!

 

There are some mysterious wires not connected to anything. Maybe that has something to do with it....see pictures below...

 

Edited November 11, 2021 by dylonwalk

[SteveJ]

Pages BE-13 and BE-15 in the FSM cover these circuits. Common points of failure are the fuse box, the steering column connector connector where the green/blue and green/white wires pass between the dash harness and combo switch, and the combo switch. 

Unplug the steering column connector and check for voltage to ground at the green/blue wire on the dash harness side. It should always have battery voltage. Also examine the connector carefully for signs that it has overheated. I've seen many meltdowns at this connector. If you don't have voltage to ground, go back to the fuse box and test the voltage to ground on both sides of the fuse.

The loose wires in the first photo are for the key buzzer. I'm not exactly sure where the second photo was taken, so I can't give an answer on those wires.

[dylonwalk]

Thank you SteveJ, I'll check that our later today. That last photo taken on the passenger side under the glove box. I added another photo of the same area. Hopefully that helps. 

[Captain Obvious]

What Steve said. The GL over at the steering column should be hot at all times. If it's not, you need to move upstream towards the fuse block.

And you don't need to check fuses by swapping them into other locations... You've got a meter, right? I bring that up because I can picture a scenario that goes like this:  You pulled the (burned out) park/tail fuse and stuck it into the cigarette lighter position. Then you checked the brake lights and they still worked. All completely true statements, but tells you nothing about the integrity of the fuse that came out of the park/tail location.  Not saying that's what happened, but simply saying it's possible.    

Here's a rough non-pretty layout of what fuses do what for the 77 and 78 years. Might help a little?

[Tweeds]

I blew about a dozen fuses and damn near burned a hole through the fuse box before I got this upgrade harness from MSA: https://www.thezstore.com/page/TZS/PROD/classic10l/12-4652 Haven't had any problems since, and the lights are a good bit brighter. I was too lazy to find the problem and fix it myself 🙃 ... 

[dylonwalk]

Tweeds, 

The harness you linked says it's only suppose to be used on the 240z, according to the supplier. Did you use it on a 280z?

[Tweeds]

18 minutes ago, dylonwalk said:

Tweeds, 

The harness you linked says it's only suppose to be used on the 240z, according to the supplier. Did you use it on a 280z?

Shoot, sorry - I wasn't being very observant. They do have a kit for later S30's, but unfortunately it's only compatible up to '77. Something about Nissan changing to a 10 pin connector by '78 (of course), and the upgrade harness is for a 9 pin connector... Here's the link, anyways: https://www.thezstore.com/page/TZS/PROD/classic10l/12-4653 You could call MSA to see if there's anything that could be done - it might be worth a try. Otherwise, happy hunting for the problem!

[SteveJ]

1 hour ago, Tweeds said:

Shoot, sorry - I wasn't being very observant. They do have a kit for later S30's, but unfortunately it's only compatible up to '77. Something about Nissan changing to a 10 pin connector by '78 (of course), and the upgrade harness is for a 9 pin connector... Here's the link, anyways: https://www.thezstore.com/page/TZS/PROD/classic10l/12-4653 You could call MSA to see if there's anything that could be done - it might be worth a try. Otherwise, happy hunting for the problem!

They also changed from the spade terminals to the round Yazaki terminals for that connector in 77. As @Captain Obvioushas pointed out in other threads, the dash to engine harness changed to AMP connectors. At least we can track those down easily.

[dylonwalk]

Well I believe I found the corporate. Looks like the Green/Blue wire got so hot it may have unsoldered itself from the combo switch. It looks a little dark around the area. Do you think it will work if I just solder it back on?

 

 

[Captain Obvious]

Well THAT doesn't look right!  Haha!

Couple thoughts. First, before you bother to reconnect that green/blue wire, have you verified that wire actually has the correct battery voltage on it? Should have 12V on it when measured to chassis ground.

And second... If that wire got so hot that it desoldered itself before, do you know why? And if so, have you changed something to prevent it from getting that hot again?

[dylonwalk]

@Captain Obvious I did check the voltage and it was getting 12.45v, is that too high? I did hook it all back up and all the lights are working again. 

I haven't done anything to keep the combo switch cooler. What do you suggest? A tiny fan perhaps hehe 😜

Edited November 12, 2021 by dylonwalk

[Captain Obvious]

12.45V is just fine.

As for keeping it cool, I suggest ice cubes. However, if you don't like the wet spots on your pants from the ice melting, you could rig up a small can of R134 and open the valve a little every now and then.

Seriously though... That desoldered wire is obviously the result of a fault somewhere generating way too much heat. The issue is if you haven't figured out what the original fault was, there's the risk that it happens again. My first guess would be failing burned up switch contacts inside that switch you pictured.

I don't want you to put it back together now and then just have it happen again in a couple weeks.