89FrontPorsche

OK, I've studied up on the possibilities that my interior lights or red safety lights may be grounding out somehow. It got dark out before I could determine if any of the interior Hella plastic fantastics with the 3-way self-destruct switch were faulty.

But fuse # 24 keeps blowing. Sucks when the dash display dies.

1) Is it most likely the contacts for the interior/safety lights that's the culprit?
2)I noted that some people have mentioned the wiring inside the A-pillar. What's up with that?
3)I plan on closely examining each and every interior light and also removing the red safety lights to examine their condition as well

With ignition off, I noted that the fuse has voltage when tested with a meter. As in, always energized. Is this the standard condition because of the rear-deck pulse release feature? No matter what amperage fuse I put in, up to 30, it'll blow. It's supposed to be 7.5 of course. So, something is grounding out, I'm sure.

Suggestions are most welcome.

Thanks,

Frustrated.

SeanR

Have you pulled all of the roof/hatch lights and ensure the wires are not touching something they shouldn't?

I had to trace this issue on a car just after a stereo shop installed new speakers and the installer screwed through a harness in the passenger rear quarter.

blitz928

Check all your interior lights in the roof panel, they are easily damaged and will ground out.

89FrontPorsche

Thanks Sean, Matt P.

Any/all help is appreciated. It got dark before I could examine each interior light. So I'm asking in advance before I go at it tomorrow. All the roof and hatch lights are removed right now but there's no daylight to see with. I have no garage, unfortunately.

A little more background: The digital dash died in its typical fashion with only the oil pressure and ammeter gauges working. I tracked down fuse #24 as the problem and replaced it and all was well. Just this afternoon, though, it blew again. I don't know when, but I'll bet it's one of those light's wires grounding out, like you and many have indicated.

Or, could be one of the red safety lamps as well, I understand. But with all the lights out, I will examine them closely and when I'm sure they are not grounding out, I'll try another fuse.

It's definitely annoying.

SeanR

Take the roof lights out and keep the contacts away from everything. If it still blows, at least you have eliminated those. Then do the doors/hatch ones. If those still allow it to blow then move to the reds. You don't have to take off your door panels to yank the reds out of the sockets, just the leather panel, reach in and grab.

If that still doesn't solve the issue, let us know and we will give you more places to look.

**Edit**

Before reinstalling the roof ones, take some duct tape or something similar and put some up on the metal part of the roof where the lights go. This will help insulate it from future shorting out.

Alan

Don't ever put a bigger fuse in.... this is a really bad idea... when you put a 30A in in place of a 5A or 7.5A its likely that the fuse is almost as capable as the wiring - if the wiring burns up somewhere in the harness you are totally screwed... just don't even think about it...

Just look at the roof lights first (including hatch) then the door lights then the door end lights (this is the order of likely failure. If any of the switched lights ever work - start with the one(s) that doesn't(dont)...

Alan

89FrontPorsche

And the answer is: Grounded out dome light wiring.

I had all the dome lights out and the primary culprit is the one by the windshield. My stupidity in putting in a higher rated fuse fried the wiring for the circuit all the way down to the circuit board. It's in a loom so, I'm not too keen about re-doing that.

Checking with a meter, the hot lead to the dome light was grounded out. Checking same at the glovebox light connection, infinite ohms.

Examining the circuit board further, found the wire that provides current to the whole shebang. Fried, with exposed copper. I can only assume the same has happened up in the A pillar and across the roof where I cannot see it.

So, chain of events was: Noted blown fuse in spot 24. Probably the dome light connectors touching sheet metal at times. Not having a 7.5A fuse, I found the next best thing, a 30A. (I have now learned my lesson). Over the next couple of days, the wire leads for the dome light would cook and melt until finally, upon opening the door and leaving it open, they melted enough to expose bare copper wiring. That contacted the metal inside the car somewhere, going completely to ground and blowing the fuse.

Naturally, replaced fuses would blow as well. for obvious reasons.

See the dome light: Tell me this couldn't have started a fire and my beloved 928 would be a burned out cinder.

And, looking down at the circuit board, I noted the fried wiring here as well. For now, I have cut this wire, taped it up, and can drive worry free but without any dome lights. When it cools down this Fall, I will make it a point to re-do this and replace my lights with the Volkswagon versions.



To everybody who helped. THANKS! Your input weighed heavily on my diagnosis and the caution about higher rated fuses is now firmly etched into my skull. I don't know, actually, what possessed me to do such a dumb thing, but I have learned. Fortunately, it's a simple thing (relatively) and I suffered by only not having dome lights. It could have been much worse.

Next time I will think very carefully before I act.

Thanks again everyone!!

Manfred

If you do a search for VW lights you should find the part numbers. I can also give you part numbers for the wire terminals in you need them.
You'll need to order three items:
1) VW Dome light
2) VW Wiring Harness
3) Wire terminals that fit VW wiring harness

89FrontPorsche

Thanks, Manfred. Much obliged.

I see you're from Charlotte. I work in Charlotte at the airport. I live in McConnells, SC, down 321 a ways.

This is my second 928S4. I had an '87 that I sold some years ago and wanted another one. It was the only car I ever missed. I plan on hanging on to this one for a long time.

Thanks again!! When I get ready to do the lights, I'll scream in your direction.

Manfred

Cool! Good to have neighbors. I'll be visiting your place of work in a week--going to Japan for my sister's wedding. (P.S. Manfred's just my rennlist ID).

Dan

Pcplod

Sean, how do you remove this leather panel??

Hilton

I'd be concerned about what other wiring was damaged when the wire melted.

I put huge current through the harness and W connector on the CE panel right through to a ground on the engine (stupid mistake using an '89 coding plug in an '87 S4). Saw the smoke and turned off the ignition immediately.

I ended up replacing about 5 feet of burned wire in the passenger footwell, and also running a temporary ground to substitute a burned ground wire. A month later I properly replaced the engine ground wire and removed the temporary one (involved getting a replacement ground wire through the firewall boot so I did it while doing intake refresh on the car).

You're going to have to trace the wiring diagram, and open up the harness anywhere that wire runs alongside other ones, to inspect sheathing on other wiring.

On the plus side, after hacking up the factory harness (taking off sheathing, pulling pins out of CE connectors, re-running wires, soldering etc.) you'll feel a lot more comfortable with the wiring diagrams and electric panel

Mrmerlin

FWIW you can remove the red door edge lights from the outside.
a small screw driver will neatly pry the housing out of the door,
then simply pull the light out of the housing .
use some silicone sealant on the harness where it goes into the rubber boot so water wont run down the harness and fill the light back up with water

Mrmerlin

the light harness runs along the right floor then to the B pillar,
up this and then to the roof. I would be best to ry and buy a used rear light harness for the car then it will be plug and play. the hatch has a big flat connector ,
make sure to add some heat shrink to all of the leads that go to every light , yes even the grounds as they can melt off the light and then touch the hot wire.
disconnect the battery when working on the roof lights no need to fry a harness by accident