2004 A6 1.9TDI (PD130) Avant - central locking remote, everything works for 30mins, then nothing, have to use physical key for entry

[A7DUO]

I've tried another driver door key control module this weekend and I still have exactly the same issue as the old unit I was blaming for the following fault.

when all known good window and door motors are connected up (as I had a few window issues too, now resolved);
Everything works with the remote keys, all door locks and estate (5th door release and lock)..... for about 30mins. Then both keys go dead, and you can only use the mechanical door and boot lock to get in and lock up again.

The drivers door passenger lock release button continues to function at all times.
So what I have been doing is disconnecting the loom from the driver's door lock unit (so I don't keep activating and then setting off the alarm on entry); and just using the manual key and this internal door lock swich for the other doors.

I really thought I might have solved it wiht a new/known good driver's door control module but its not that at all, as the problem exactly the same - with dead keys actuation after 30mins again (and I tested/replaced both batteries in my keys too).

Any ideas appreciated - I expect an issue somewhere in a loom or the comfort module; but just curious if anyone else ever had the same and managed to fix it. Thanks for reading this.
MS

 

[spartacus68]

Have you scanned the car with VCDS? Had my own share of issues chasing window regulator fault on wife’s BMW i3 for best part of 6 months. Turns out water pools in door and rots out wiring connector. Traced that with ISTA.

Back to your predicament, what I can’t work out is intermittent fault. Is central locking electronic or vacuum pump? Any history of water ingress in car?

 

[A7DUO]

Thanks for your response, very handy. Yes and the garage that diagnosed it for me, is used to reading VAG-COM, at last service pointed to a fault at the time in the driver's door and reset a few historical faults that had never been reset, and haven't come back since (but I have changed the window regulator and master door controller with OEM originals since) - so I guess it could be wiring loom in that door somewhere.

Yes the car had the wet undercarpet fault when I got it (until I cleared the drainways up front permanently and resealed the cabin filter box) - dried it all out. Tried a new/known-good comfort module - but none of that seemed to make any difference and I'm back on the original comfort module now.

Yes its weird how everything works perfectly, including both keys, when first connected up again and then 30mins later the the wireless keys behave dead again. Its almost like some resistance builds somewhere in a circuit and knocks out its ability to receive a an RF signal.

Also I should say the central locking is electronic, not vacuum pump

Annoying as this is literally the only fault with my low miles super-reliable and efficient PD130 Avant (except the rear-most boot courtesey light: when I must have pinched a wire somewhere when repairing the head-lining - and I'm not taking that lot out again), I can live with that and using a key to access the driver's door when everything else works so well on this car. Only looking to repair the remote key access to satisfy a future owner (as I am looking to replace it with an estate car from Skoda next).

 

[spartacus68]

Okay - water ingress can play havoc. I repair outboard engines in my spare time and of course outboard manufacturers don't used tinned cable, and neither do automotive companies. I'll bet somewhere in that loom there's oxidisation (the copper oxidises) and you'll get a break in continuity. Having said that - it tends to simply stop working.

Similar sort of thread here but on C4 chassis. https://forums.ross-tech.com/index.php?threads/2629/

Even if you sell this car and get a Skoda - VCDS is very handy. VAG are doing everything they can to restrict DIY repairs. Even the new Golf - you can't swap out rear pads without ODIS. They also disabled ErWin unless business use. You can get VCDS (3 VIN version) for just over £200 from Gendan. That gives you lifetime software updates and of course you can post scans on RossTech for more detailed and forensic fault finding. Of course you'll need nan old laptop to run it.

 

[A7DUO]

Thanks very much - that link is an outstanding journal of a very similar problem, almost identical to mine. Thanks in that owner's case the Comfort module swap worked. In my case that did not work, so points to wiring short to antenna or loom somewhere.

Thanks for the recommendation on the VCDS from Gendan. It is probably high time I invested in one for home use. Seeing as I have a PD130 Superb (which to date has been fault-free and I've owned it 4 years and covered 40k miles in it in that time too), and yes if I add a 2.0TDI Superb to the line-up in future - it sounds as though it would be very useful for that too.

regards MS