Near Disaster Installing Climate Control Unit LEDs

[LucaScali]

So I decided to replace the perfectly fine and working bulbs in the heater control unit with bright, supposedly high quality LEDs. The draw on the LEDs is .3 watts compared to 1.2 watts for the original incandescent bulbs. No problem, right?

Bulbs went in fine, but when i turned on the lights to tests, one of the wires almost instantly began to smoke and caught fire. It freaked me out, so I sprayed it with fire extinguisher I had in the car. This caused a huge, powdery mess and I probably breathed in way too much of it, but it turned out to be pretty easy to clean and the the damage was contained to the one wire and bulb holder.

The lights were working normally before the attempted swap, so not sure what caused the issue. I've never run into any problems with LEDs. I'll need to replace whatever part includes the wiring for the lights at either end, but I'd like to understand what caused the problem before I try again (or test the light that goes on with the fan). I've removed the bulbs, so I assume it's ok to for now.

[eflight]

Some LEDs with contacts on both sides create a short because of the way the contacts are connected on the LED board.

[Balisong]

We all need to fuse the dash lights.

[Discseven]

I certainly don't know LED inside and out but... installed LEDs in my kitchen and it was a science project. I forgot what boxes I installed to make them work. Point is it was not plug & play. LEDs I installed called for some sort of "electrical converter." Perhaps this is something to look into. If you're an LED pro, I digress

[LucaScali]

I have high powered LEDs everywhere except in the gauge cluster and the wedge bulbs in the heater control unit. Never had a problem before. Took me by surprise; God only knows what might of happened if I hadn't been able to quickly put it out. Balisong is right.

eflight, could you please explain what you mean? How do I avoid bulbs with the wrong bulb configuration for this application? These are the bulbs in question:

https://www.amazon.com/dp/B07T9BB4BM

[LucaScali]

Just saw this in the reviews:

" The LED is incorrectly designed and short-circuits when you use it. The foot has 2 contacts on each side, with plus and minus on each side. And this is the mistake, because you have to have plus on one side and minus on the other side. I solved it by milling away a plus on one side and minus on the other side and then they work very well. "

[LucaScali]

So the damage is a bit worse than expected. Not sure what I'm looking at. Could someone please tell me what part(s) this looks like and at what point it connects to the larger bit that traces up to the ignition switch. Is it all one piece? I'd like to get it off so i can start to clean things up properly. The powder is everywhere.

[GH85Carrera]

Originally Posted by Balisong

We all need to fuse the dash lights.

First do this! The lighting circuit from the factory has no fuse! If your system had a fuse, it would have popped the fuse, and the wires would still be fine. More than a few 911s and 914s burned to the ground due to no fuse in the dash lights!

Also check the front condenser blower, If there is no fuse unplug it until you have a change to fuse it!

The footwell blowers need a fuse!

We all like to think Porsche engineering is top notch, but the electrical depart were drunk when they designed the 911 wire harness.

[pmax]

This is also a stark reminder that solid state devices aren't always better than the tried and true OEM designs.

[pmax]

Originally Posted by LucaScali

So the damage is a bit worse than expected.
...


...

I would keep the battery disconnected until this is all sorted out.

[LucaScali]

Good advice, thanks. The battery is disconnected. I need to remove this stuff so I can move the car and vac the interior, and order replacements. Could someone please tell me the what part or parts I'm looking at and the best way to remove to make installation of new wiring easiest? I mean I could just cut the whole thing off where the damage starts and tape it off.

Incidentally, while it doesn't look like a big deal, I'm trying get Amazon to cover this damage as a matter of principle. At least two other people had reported the problem with the bulbs. If I could figure out what parts I need, it would be helpful. I'm not sure what I'm even dealing with.

[dg567]

remind me never to do that

[LucaScali]

Ok, I'll remind you. Can you help me figure out which parts I need to get it sorted? the heater control unit takes three bulbs. one of the three survived without any damage; think it's the fan light. But it looks like there are two fried light wires and one with a larger wire that's relatively intact. Where is that one supposed to go? I'll have another look at it later tonight.

I guess I should cut that mess off where the damage starts for now. No point in trying to unravel it.

[timmy2]

What year is the car? It makes a difference in the wiring.
Hope the lamp sockets are ok, they are NLA…

[LucaScali]

It's an 87. They are not, unfortunately. 2 of 3 are toast. I think part of it is 91161217201, which as you said is NLA, but I found one.

[LucaScali]

So the extra socket belongs to the ash tray light. It's perfectly intact, at least. The other two sockets are kaput. I cut the damage off where a blue and gray wire meet the ignition switch harness, and taped everything off. I reconnected the battery and tested the acc position with the fan blowing, and everything seemed fine. Is there anything else to look out for before I start the car and give the lights a try?

Now that the patient is stable, I'd appreciate help in determining what parts are required to put everything right (and the best/easiest way to do it now that I've cut wires that seem to be part of the ignition switch wiring harness). I need to wire in the sockets that go to either side of the control unit, and get power to the ash tray light. All in all, not so bad. It could have been a lot worse.

[rothaus]

The sockets for the fan light have the plus on one flat side and minus on the other flast side. If you look at the original glass bulb, one wire is bend to one flat side and the other to the other.

The LEDs you got have the plus at one end and both flat sides, and the minus at the other end and both flat sides, and therefore make a short.

See image below

Original bulb



LED


Also to prevent any burned wires here is a pre-wired fuse



http://carmagic.us/fuse.html



Hope this helps
Engelbert

[LucaScali]

Thanks, Rothaus. A couple people had actually reported that problem with the design. I should have read the reviews, it was right there.

Now I need to sort it out. If anyone could list the parts needed in this situation, I'd appreciate it. I could guess at it from the PET, but it's not entirely clear. Looks like 91161217201 has two sockets and two spade connectors that presumably connect to the ashtray light, but don't see how it gets power from the ignition.

[timmy2]

Doesn’t get power from ignition, porsche used the ignition harness as a convenient conduit that runs from the light switch connection 58a terminal to the ashtray, from ashtray to the hvac lights.
Grounds were run separately.

[LucaScali]

Thanks, Timmy. So the wires that connect the light switch to the ashtray are an integral part of the ignition harness, then 91161217201 for the hvac lights? Is that right? Where do the wires from 58a connect to the ashtray?