Impeller for central locking mechanism

[SnabelAir]

Hi guys!
I hope everything is well with you and that you perhaps can help me with a small issue. I have just bought a used Audi A3 Sport from 2001 and it works like a charm. However, the central locking mechanism isn't working. That is, the transmitter on the key can transmit and the receiver in the boot receives the signal and starts trying to lock the doors. I can hear the mechanism trying to work in the boot, its a small "buzz" from inside the black plastic box on the left, however the locks on the doors never engage.

The previous owner told me that he had done some quick research in the issue and had come to the conclusion that "the impeller needs to be replaced". I understood it as that the impeller is building up pressure needed to actuate the locks in the doors and somehow mine was broken or at least not working.

1. What do you guys know about this? Could it be the "impeller"?
2. Is it hard to replace for a non-skilled person (me)?
3. Where do I get a spare part? I've tried Euro Car Parts | The UK's Number 1 Provider of Car Parts Online and In Store, but they didn't have anything like this...

Thanks for any help or guidance!

[zollaf]

find the pump, pull the pipes off and make it operate, see if you get a vacuum and pressure. could be the impellor but is most often an airleak in one of the pipes.

[SnabelAir]

Hello again and thank you very much for taking time to answer me.
Yday I realized I cannot access the air pump, only see it, please see the attached image. How do I remove the lower panel to access the pump?

[acmo]

Have you got it out yet?

[SnabelAir]

Oh, hi! Thanks for checking!
No, I never managed to loosen the bottom panel. Today's been a bank day to the plan is to take her down to the garage tomorrow morning. I think its better to leave these things to people that know stuff more than me! Thanks anyway!