Hello everyone, I've just bought an Audi A3 2.0TDi Sport 2005 ( 3 door 8p). Its got a few minor cosmetic faults but it was extremely good value. However the most annoying problem is the central locking. I'll do my best to explain the problem:

Both key remotes don't seem to recognise the car at all - they do nothing. The light comes on the remote so I presume the internal batteries are fine. But it's also a real struggle to open the car manually with the key. It will lock everytime with a left twist (confirmed by indicator flash), but a right twist will only open the car after several dozen attempts! The lock springs feel ok, and it doesn't feel slack or broken. it's a total lottery - no special knack or technique, it's just got a mind of its own. It opened first time once, that was incrediable!

When I eventually get into the car, both keys work perfectly in the ignition and starts the car every time (so no problem with immobiliser). Curiously when key A is in the ignition, key B is able to manually open and lock the drivers door every single time - the mechanism appears fine. So I don't think the physical door lock mechanism is at fault.

I've tried several techniques of resyncing the remotes, but this doesn't work. Ive read something about a "central locking pump" in the boot, they seem fairly cheap on eBay. Could this be the problem?

Please remember I don't know much about the cars history. Bought from a small independent garage, did cost me much and used this fault to negotiate a big discount. Any help would be greatly appreciated - I look like an idiot trying to get into my car at the moment in the pouring rain!

Ok quick update. Had a look behind boot liner which revealed a "convenience module", and not a vacuum pump like I had been expecting. The convenience module looked clean, not water damage etc.

Would changing this solve my problem? They seem fairly cheap on eBay (and the part numbers match). Am I going to have to recode anything if I install a new module??

I've also discovered a technique to opening the doors manually on my car. Turn the key once left, a subtle locking sound is heard, turn it left again and a louder locking sound is heard. Reverse this process turning the key to the right twice opens the door . It's not foolproof but works 70% of the time.

Can someone please help me?! What else could be wrong if it's not the convenience module??