1.9 TDi a/c problem - any ideas?

I've recently had a leaking condenser replaced and the system re-gassed which fixed it for about a week, then no cold air. Took it back to the garage who could find no fault but said they had reset the a/c ECU (its basic climatic not climate control, so is does it even have an ECU?). Anyway it was blowing nice and cold again.

10 days later and again, no cold air. Then after about 10 mins driving It starts working. I've now realised that if the a/c is used daily it seems to be fine but if the car isn't used for a few days, it takes about 10 minutes for the a/c to start blowing cold air.

I reckon the basic system is OK but something is faulty in the control system but have no idea what. Has anyone come across a problem like this before?

Edited 13 July, 201411 yr by goosander