Hi friends

I'd like to ask you if you have any guess what my problem is. I haven't been able to have a decent A/C on my Q7. It blows fresh air, but not a very cold air as it should be. Here are the symptoms:

When I turn ignition in the very morning (system is cold), AC wont blow fresh air, just normal air. It may take 2 or 3 minutes until it starts blowing fresh or cold air. Problem gets worse the vehicle stays for several days without moving, then AC will take more than 5 minutes to start working. So, as system isn't hot and fans are working fine, I think it is not a condenser problem.

I have already emptied 134a gas and filled again and the problem is still the same, just fresh-cold air (16-18 celcius I think), and not a super cold air (13 C° or so).

Something strange I have noticed: If I push the low pressure valve to let some 134A gas escape for 10 seconds, then AC works like a charm, the air is really cold. But it only works for some minutes and then everything back to normal.

I wanted to buy an AC compressor for $200 bucks at ebay, but not sure it will fix the problem.

Thanks for your comments. Have a nice day!