MP4.2+6.0

It might be a bad heater control valve, which likely would not show codes. You could try bypassing it or plugging the heater lines to test.

Amiko Tsanava

ok. How can I bypass it? Or what can I plug?

MP4.2+6.0

It is in the plenum area (under the cover) on the passenger side. You would have to improvise something with some tubing, fittings and clamps to bypass. Or, just figure out which hose is the hot water supply from motor, remove and temporarily cap both that hose and whatever you pull it off of--so coolant doesn't flow in reverse out of the heater valve. Again with some improvised plumbing type fitting and clamps.

Johnnyb2451

I am having this issue as well. An indy I know tore the whole dash apart and checked the head unit and said it was functioning properly (didn't charge me thank goodness). Mine was also low on refrigerant, however, it staying full now. The air now blows cold consistently only on the driver's side when kept on max cool. I have drove this car like this for several months, though when it is over 80 degrees or so, it does not blow cold enough to keep me comfortable. The other day the air cut off completely and I had to turn the controls off and back on again to get it to work. My '04 now has 204,000 miles on it, I quit taking it out of state but is still reliable.

ModestW12

OP, I had a the inverse of your problem way back with my 2007 W12 that required replacing of components. I've linked that thread below and maybe the information there can help you diagnose:
https://www.audiworld.com/forums/a8-...g-air-2796774/

I thought I was having your current problem (blowing warm when it should be cool) with my 2008 W12 recently but I got the AC recharged and the recharge either masked some other underlying issue very well or the low charge was the cause as the cooling seems to be working well now.

dvs_dave

My AC was acting up too. Not as randomly as described in some cases here, but it was taking a long time to cool things down. After 13 years I figured it was time to get it evacuated and re-charged with fresh compressor oil and R134a (1.32lbs / 600g is factory spec) at a local shop for $120 which I thought was reasonable. Anyway, AC performs much better now and cools down much quicker.

I toyed with one of those cans of r134a, but they just introduce air and moisture into the system as you can't (legally anyway) purge the connection pipes before connection. And what with the system having a variable volume compressor, it's impossible to tell when to stop filling so there's a real risk of a compressor killing overcharge, even with hi/lo pressure guages attached. That's why they're filled by weight, rather than old school fixed volume systems (like a traditional AC system in your house) which can be done safely by squirting a can on r134a in and monitoring the hi/lo pressures.