Alex2.7T

I have a 2001 Audi A6 2.7T, and the A/C wont blow cold air when car is iddling. It only blows cold air when car is moving, which I believe is very obvious since car sucks more air while moving. Which makes me believe the refrigerant is low, is it okay to just buy a 134a can and top it off through the low pressure port? how will I know how much more refrigerant is needed to top off system?

Harleyguy

The brand A/C Pro can be purchased at many stores (Walmart, Auto Zone, NAPA, etc.) It comes with an install kit (hose and gauge) The instructions are very explicit and tell you how to check the system for correct amount of refrigerant/ pressure. Your symptom indicates low amount of the 134a. This method will not search out leaks. The product also contains compressor oil. Not disagreeing with george here but at a cost of around $35 you might solve the issue. At least it will do no harm to the system. The adapter on the hose will only fit on the correct port (low pressure side) so you don't have to worry about the can exploding in your face.

BernieBenz

Georgeb: Yours is a "Henny Penny, the sky is falling" response if ever there was one! Without a system checkout with gauges, his suppasition that the system is low on refrigerant is the most likely synerio. Just BTDT on my '02 2.7T @165K, AC never prior serviced. I have a gauge set but no 134 adaptors, so bought a low side adaptor and a 14 oz can of 134A and. with engine running and AC on full, started adding gas while feeling low side temp. Expecting low side to frost up if overcharged, never happened. Added full can and like new cold air and no frost up. Good enough, DFWAB!
What's this "destroy the system" BS?

4Driver4

Bad advice.

If the AC is blowing warm due to a fan unplugged or something simple, adding refrigerant will overcharge the system and it won't work as efficiently...even after the real problem is found. These cars run on a very specific charge. Too much is as bad as too little.

Check the radiator fans to make sure they come on with the AC.

twopedalwarrior

a more suitable answer might be that the clutch on the compressor is going. low rpm starts don't always engage a worn clutch. When you mention the ac works under load sounds like the clutch kicks in when the rpm's get going