Question about A3 8P door wire loom repair

[Gary-A3]

My 2007 A3 (had it since new) just crossed 100k miles and it has been the most reliable car I've ever owned. But it hasn't escaped some minor issues, like the decay of wire insulation on door wire looms. About 4 ~ 5 years back I'd had some pesky problems with the window controls and door locking, and discovered it was the driver's door wire loom. The insulation had stiffened, cracked, and caused stress to the copper wire filaments resulting in breakage. I was able to fix the troubled wires and all has been OK, with only 1 exception. The left rear door window. I have enabled fob control of the windows (press+hold on unlock will cause windows to roll down, and press+hold on lock will cause windows to roll up). The odd thing that happens when rolling up is sometimes the left rear window will do the opposite--it'll go down instead of up. And it will be about 4". Basically the window will no longer be responsive for auto open or close. However, I can clear it by cycling manual full open and close and the window will answer to auto open/close. I suspected that it might be a wiring problem but it didn't annoy me enough to try troubleshooting.

But now there's another problem. This happened about 6~9 months ago. I discovered my left rear door wasn't locking. Clicking the lock button on my fob would cause doors to lock but there would be no hazard flash or sound. And that's because the left door didn't lock. Somehow, miraculously, the problem went away and the door went back to locking/unlocking properly. That is, until now. I'm having this problem again. Also, I discovered that the driver's door lock controls won't force the left door to lock either.

Since this issue cleared up and then returned again, I'm guessing that it's the wiring and not the lock actuator. Is the wire loom repair kit that's used for the front door also the same for the rear door? Here's the kit I intend to buy: Prewired Door Repair Kit Harness Loom for A2 A3 A4 A6 TT.

Edited July 11 by Gary-A3

[Gary-A3]

Well, I may have lucked out.

I'd cleared the VAG COM codes and the door codes came up again.

So, I went to inspect the wire loom of the left rear passenger door. I detached the boot and examined the wires. From the very narrow viewing zone it appears that most of the wires are intact. But I did notice one had insulation cracking, just one running perpendicular to the wire length. I couldn't see very well and wasn't able to detach the black multi-wire plug. I put the boot back and... the door lock works again! It must be a faulty wire and I just need to secure it back together.

Edited July 12 by Gary-A3

[cliffcoggin]

Broken wires are a common problem with A3 doors, and possibly other Audis as well. The fractures are usually in the rubber bellows between doors and frames. A search of this forum will reveal many occurances.

[Gary-A3]

5 minutes ago, cliffcoggin said:

Broken wires are a common problem with A3 doors, and possibly other Audis as well. The fractures are usually in the rubber bellows between doors and frames. A search of this forum will reveal many occurances.

Yes, I am aware of that (from the first time I had to troubleshoot issues cropping up due to the wire loom insulation cracks on the driver's door). It appears that wherever Audi sourced the wiring, substandard wire insulation was used that unfortunately doesn't turn up with problems until quite a few years past the warranty expiring. I hope Audi corrected this glaring flaw and uses insulation for wiring that's far more resilient and will last far longer.

It took me a good while, but I did finally find a video where someone demonstrated the release of the plug from the socket. There's a black tab on the back side of the plug that's pretty much impossible to video capture while inserted. By intuition, I expected the purple portion of the plug was some kind of release tab... and it's not.

 

Anyway, given how this is the second time I'm having wire loom issues, I'm thinking I should buy that loom repair "kit." There's examples of it costing over £55 that comes with the loom segment, pre-stripped, with crimp connectors and a wire sleeve. But I've found on AliExpress.US a version that's just the wire loom segment, pre-stripped, and nothing else. All good, as I have some wire crimps on hand.

Does this look legitimate to you?  Prewired Door Repair Kit Harness Loom for A2 A3 A4 A6 TT.

[cliffcoggin]

24 minutes ago, Gary-A3 said:

Does this look legitimate to you?  Prewired Door Repair Kit Harness Loom for A2 A3 A4 A6 TT.

I have no idea, but I am a great believer in the saying that if something looks to good to be true it generally is too good to be true. £5 for a wired connector is ludicrously cheap.

[Gary-A3]

4 hours ago, cliffcoggin said:

I have no idea, but I am a great believer in the saying that if something looks to good to be true it generally is too good to be true. £5 for a wired connector is ludicrously cheap.

Well, with shipping it ends up being about $10 USD. I figured it's worth ordering just to check out. If anything, I could release the wires and use them with the OEM plug (which is still in great shape).

[Rybrook]

I have 2 wired connectors, ready for when mine fail.

I had the issues with the drivers door, C/L and puddle lights not working, after inspecting the door it turned out the actual lock was malfunctioning, worn micro switches made the car think the door was permanently closed.

 

Good luck with your fix.

[Gary-A3]

17 minutes ago, Rybrook said:

I have 2 wired connectors, ready for when mine fail.

I had the issues with the drivers door, C/L and puddle lights not working, after inspecting the door it turned out the actual lock was malfunctioning, worn micro switches made the car think the door was permanently closed.

Good luck with your fix.

Smart idea.

I fixed my driver's door wire loom twice, the last time being about 4~5 years ago. It's curious... only 3 wires had frayed, and one had separated completely. The other wires appeared OK, although I could tell the wire insulation was getting a bit stiff. When that fix I made worked, I then checked the other wires for where they tend to bend and reinforced them with a little electrical tape in hoping of "holding off" the future insulation cracking.

The left side doors of my A3 are the most heavily used (USA spec)... and so I suspect that's why the doors on the right have been fine--not getting flexed much. It does make me wonder if that's a time-bomb, though. With rather minimal flexing, perhaps the insulation will further stiffen and then tend to break suddenly at some point (rather than a few filaments broken, weakening voltage across the wires and creating intermittent behavior).

Did you inspect the wire looms of the other doors on your A3? They all look perfectly fine and feel reasonably flexible?

Edited July 12 by Gary-A3

[Rybrook]

2 minutes ago, Gary-A3 said:

Smart idea.

I fixed my driver's door wire loom twice, the last time being about 4~5 years ago. It's curious... only 3 wires had frayed, and one had separated completely. The other wires appeared OK, although I could tell the wire insulation was getting a bit stiff. When that fix I made worked, I then checked the other wires for where they tend to bend and reinforced them with a little electrical tape in hoping of "holding off" the future insulation cracking.

The left side doors of my A3 are the most heavily used (USA spec)... and so I suspect that's why the doors on the right have been fine--not getting flexed much. It does make me wonder if that's a time-bomb, though. With rather minimal flexing, perhaps the insulation will further stiffen and then tend to break suddenly at some point (rather than a few filaments broken, weakening voltage across the wires and creating intermittent behavior).

Did you inspect the wire looms of the other doors on your A3? They all look perfectly fine and feel reasonably flexible?

I have a 3dr, my right drivers door is the most used especially if i have the kids in, I didn't bother looking at the passenger side as everything was working as it should.

At least they didn't use the biodegradable plastic for the wires like Mercedes did, my old c class engine loom was all falling apart when I passed it on to some unsuspecting buyer.