cwitt

I was nosing around inside my left headlight assembly, because of a high beam warning, and noticed that most of the wiring insulation is very brittle, and cracked in places. No discoloration or deformity (signs of shorted/overloaded circuit), just dry and rotten looking.

The wires for the additional high beam (bi-xenon lights) were so bad that I had to remove a large length of the wires, solder in replacement wires, and protect the remainder with heat shrink tubing.

Looking around by the connector pigtail on the car, I see that pretty much all of those wires have brittle/cracked insulation too.

Is this common?

If it's happening on these wires, I have to think it might be happening elsewhere in the car, and that it could represent a serious fire hazzard. FWIW, it's a 2005 Cayenne Turbo.

Thanks,

Curtis

KevinGross

The sheath shouldn't be dried and cracking. I'd want to understand why that is happening: mostly likely a heat issue. Sheath is available from Wurth in a range of sizes, by the meter.

Kevin
Catellus Engineering

cwitt

Just to be clear on terms, I'm talking about the plastic insulation that's part of each ~16 gauge wire, not a loom or wrapper that binds multiple wires into a harness. AFAIK, there's no way to replace insulation on a wire once it's damaged/gone.

I would expect this type of cracking in a VERY old car, but not a 2005. I don't even see this type of thing in the wiring on my trusty 1985 Carrera!

Kevin, I agree that it would most likely be caused by heat, but again, there's no discoloration or deformity suggesting an over-current situation. Besides, I find it hard to imagine that every single wire in that headlight pigtail has experienced that serious of an over-current situation.

People say that the turbos produce immense amounts of heat under the hood -- could it be that my engine compartment wiring has been slow-cooked by high ambient temps over the years?

KevinGross

Curtis, it's certainly not normal. If the insulation on the wires is brittle and cracked, they should be replaced. Your options would be to buy the harness from Porsche, or use good quality wire and connectors (eg again, from Wurth) and build your own.

As to what is cooking them, as you note it could be ambient temp in the compartment or could be a current draw problem. Chemical abuse is another possibility. I suspect you're going to have to do some testing to figure out what it is. Current draw is easy enough to check. Ambient temp could be checked by putting your hand into the compartment area after a spirited drive, or you could use a pyrometer. Chemical contact is probably an observation: periodically check the wires for oil, etc. after a drive.

Hope this helps.

Kevin
Catellus Engineering

ciaka

I saw the same thing. 2005 CTT.
Once removed headlight to replace failed cornering bulb, looked into the headlight compartment (removed cover first..lol).
Once there, observed that the wires coming from each bulb, into the main connector that gets connected to on car side, all those small gauge wires are extremely brittle. No discoloration (indication of overheat). No stress, no chemical usage.
Appears to me that the wires are not designed to take prolonged high heat exposure, and over time the plastic shielding degrades to the point where any physical contact (even wire to wire during normal driving), can knock off small sections of the wires and cause them to short together. This would certainly explain some electrical mysteries that some cayenne owners talk about, batteries going dead, etc.

If you take the time, remove any of the headlights, remove cover and look at the wires, you may see some cracking, however I was able to see several wires appearing pristine but upon the smallest touch, crumble a tiny section of insulation off. The only way I see to repair is to either purchase the connector with wiring attached (IS THERE A PART FOR THAT FROM PORSCHE????), or to replace the wiring (soldering involved with heat shrink tubing and wiring that can withstand the climate - long job).


Anyone else can confirm this? To me starts looking like a defect/recall candidate.

flyjets

This is due to Biodegrade wiring insulation required under German law.

BMW Mercedes etc also have the same issues.

My Xenon shorted the other day 2 months out of warranty and 1 week after I bought my 997 TT great timing.

Replacement with wiring harness can be around $2,600 with OEM components.

This also happened on my SL55 AMG several years ago.

It will happen to all German cars especially if they are exposed to the Florida heat.

Ian

cwitt

It's been a year since my original post, so I thought I'd circle back with an update. I did remove the bulb access cover from my left headlight, and replace a couple of the worst looking wires, by soldering in replacement sections, with heat shrink tubing over the solder joints.

I have since had both fender liners out, as part of removing the front bumper cover to replace both horns. While they were out, I got a chance to examine the upstream wiring. The pigtails show just mild cracking on the insulation, but no missing insulation. The main harness shows no cracking whatsoever, and is still nice and flexible.

Other wiring inside the engine compartment looks great. I got a peak at the radio harness while replacing the cabin air filter and it looks great too. Lastly, I saw all kinds of wiring when I had the D-pillar and rear headliner out for hatch/glass strut replacement, and it all looks great.

It almost seems as though the pigtails and the wiring internal to the headlight housings is of a different spec than the rest of the car.

sapman

Was getting worried that this would lead to the same issues the later w124 Mercs had. The biodegradable wiring harnesses all had to be replaced.

catamount

I'm about to embark on this joy with my '94 E320. The main engine harness and the ETA wiring are both shot. I'll replace the harness and plan to attempt a rewiring on the ETA. There's a really good write up on benzworld.org about doing the ETA.

sapman

I don't think it is too bad of a job. My 400e already had the upper harness done when I bought it and didn't exhibit any of the electrical gremlins that point to the others being in need of a change.

Aside from this issue, I absolutely love the W124. Such a solid car. Would love a 500e but a good one is hard to find and the parts are quite expensive.

endless_corners

500e's have really started to climb in value again.

TimATC

Here's a look at the harness from my headlight. Both sides replaced with new parts. Also replaced headlight ballasts, and bulb. Worked for a bit, now....not so much. We'll back to the shop on Monday.

Manitou

I understand the biodegradable insulation used on German cars is a big problem. Has anyone tried simpler solutions such as clear plastidip spray? Really dose a whole harness and see how it does? I don't want to cause a fire of course, but how much worse can we make this.. I mean.. There's bare wires touching!

Manitou

In case anyone comes across this, I used black spray plastidip. So far so good.

deilenberger

I hate to rain on a parade - but if it was me (and it's not..) I'd replace that assembly. How does PlastiDip hold up to heat? It seems fairly obvious the insulation is failing at that assembly due to heat, either from the headlight, the connector, or due to undersized wire heating up. I have no idea of PlastiDip's ability to resist heat, but I can't imagine it's any better then the original insulation.

BTW - tie-wrapping the wires into a bundle will simply concentrate heat at that point, and possibly lead to a short circuit. Hopefully the fuse will protect the rest of the wiring.