Central Door Locking, etc.

[Carloski]

Wondering if anyone can throw light on this problem.  My 2008 Mk1 Superb has done less than 60k miles, regularly garaged, no water ingress, ever.  I just returned from North of Scotland (weather dry, cold at night, very hot in day) where the central door locking stopped working and I had to lock and unlock using the key.  Replacing the 10 amp fuse rectified the fault for a short period, only for it to blow again.  Within 24 hours of returning home and leaving it in the garage for a couple of nights, the fault rectified itself (IE 'door open' indicator light on the panel went out of its own accord).  Its just spend a day in a VAG workshop where all the relevant wiring has been tested and everything is at it should be.  Door circuit faults were recorded on the data logger, but that does not identify exactly where the fault might lie.  Any ideas?

Just one final comment if it ever happens to you.  When the door fuse blows the fuel filler flap won't open which is not very clever when the nearest garage with spare fuses is a two and a half hour round trip away ... and you are low on fuel.

[Taede]

I'd check the carpet just to be on the safe side.

 

That said, your car will be around 14 years old. It could be that the insulation around a wire has worn in a way that it only shorts in certain conditions. Wiring in in the door-hinge area will be most suspect there.

It could also be that electronics in the actual lock units have given up the ghost, given intermittent faults. Lastly, I'd check the convenience control unit under the passenger seat carpet, though I'd imagine the VAG would be able to tell if that's knackered.

 

As for the fuel filler flap, you can always open the boot with your key. There's a manual fuel flap opener accessible from inside the boot. You'll find it behind the bit you also look when you need to replace a bulb on that side at the rear.

[gfinneran]

Door lock on its last legs probably especially its original, they will all fail eventually with cracked solder joints, if you haven't addressed the the water ingress points with corrective action you will get water in the car eventually and subsequent electrical issues related to same, these cars all leak not a matter of if but when, have a good read of the thread stickied at the top.

Door locks can be got on ebay but some are of dubious quality pays your money and take your choice in that regard.

[Carloski]

Many thanks Taede and Gfinneran for your ideas.  My latest thought  is that some component in the circuit was affected by high temperatures in Scotland (no kidding) - I remember laying a towel across the top of the dashboard because you could have fried an egg on it.  Since returning to England the cooler temperatures may have reset the problem.  This may seem a bit daft but many moons ago a friend with a Vauxhall had problems when it stopped on hot days, after sitting at the side of the road for a while the car easily restarted.  The problem was eventually resolved by putting the ECU in the oven (on a low setting I might add).  At higher temperatures the ECU stopped functioning.  Changing the ECU solved the problem.  So I wait to see if the problem recurs on another hot day.

With regard to water ingress, no sign was found in doors or under carpets.  A few years back I did find water sloshing around under the battery, none had reached the car.  After draining it and cleaning the channel I scrunched up some stainless mesh under the battery to protect the small drain hole from leaves.  This seems to have worked. 

Thanks again, will keep you posted - here's hoping for a hot summer.

[numskull]

If it’s never had the plenum chamber fix, it’s a 100% fact; it will leak and given the issues you now have, it already has at some point and it sounds like the convenience unit is already damaged.

You also need to remove the two rubber drain bungs in the chamber too. Your method of trying to stop debris blocking it will not work, because it’s the smaller debris which initially blocks them. Your mesh installation will will make the problem worse. I spent over £1,200 pounds having the convenience unit and complete wiring loom replaced about 10 years ago, including the section to the parking sensors, which they also fully resealed. I checked the loom and unit today and it’s still as new.