Audi Repair: 2002 A4 1.8T, vag com, pressure switches

Question
The A/C on my 02A4 does not seem to work, VAG'n shows:
01592 - Air Quality Sensor (G238)
37-00 - Faulty

Looking at display group 001 in VAG shows a constant pressure of 21% in field 3 and 5 bar in field 4. Somebody mentioned to me that overload safeguard has been triggered and needs to be reset.  This is quite possible since engine seized earlier and was replaced with a used engine at small shop.  How do I reset overload safeguard on the AC compressor?

Answer
You should be able to reset the faults using the VAG-COM.  If they come back, then it is time to check the pressure switches and the AC compressor itself.  I am not sure where the values need to be, but an air conditioning specialist will know where the boundary conditions are.  Let me know,  Jan