AC issues

[Brav]

I searched and didnt come up with much. I had intermitten AC issues, with warm air coming out. Then it went away, blew cold, after fidgeting around with the controls, raising temp to max then min, shutting off and on.

Then 3 days ago, its just full warm/hot air. I noticed before that even on a cool night, the vent air while on econ that comes through is quite warm... maybe the engine just runs really hot and heats up the ducting.. is this normal?

Anyhow, I had the system serviced, evacuated and topped off with 1.75lbs of R134, which was pretty low. Now it stopped working, almost completely. I can hear the compressor engage and dissengage as I hit the econ button, but still barely cools the air...

Any suggestoins, or is it new compressor time?

[mmaturo]

I searched and didnt come up with much. I had intermitten AC issues, with warm air coming out. Then it went away, blew cold, after fidgeting around with the controls, raising temp to max then min, shutting off and on.

Then 3 days ago, its just full warm/hot air. I noticed before that even on a cool night, the vent air while on econ that comes through is quite warm... maybe the engine just runs really hot and heats up the ducting.. is this normal?

Anyhow, I had the system serviced, evacuated and topped off with 1.75lbs of R134, which was pretty low. Now it stopped working, almost completely. I can hear the compressor engage and dissengage as I hit the econ button, but still barely cools the air...

Any suggestoins, or is it new compressor time?

Oddly i just posted on another thread that i have had 7 HVAC control units in my car and this was kinda why. It would work fine for about thirty minutes (on an 80 degree day...cooler it would not do it) but when it reached temp (that it was set to) a damper somewhere would close and although the compressor was running or restarted, and the interior was warming up, the damper stayed close and keep any cold air from actually coming out no matter what setting was selected...happened over and over even after a new unit would work a few months then it would happen again. Problem was that it was nearly impossible to replicate since from a cold start it worked for just under an hour...a tech can't really cruise around that long...but once it did happen it would not reset or let cold air back out unless the car sat for more than a couple of hours.

Well the last control unit finally did the trick and has been ok for almost two years now...yep just jinxed that too i'm sure.

Your problem may be using the econ too much or it is getting confused...i never use it no matter the weather though. I have never used just the vent as the engine does run hot so air is always warm coming in so i do always have some level of cooling going unless it is winter then its heat but still have system going to help remove humidity (like on a snowy day).

[Brav]

Well 2 days after posting, all went back to ice cold and no hint of not working.. go figure. Must be some kind of electrical issue. Hopefully it stays fixed

[Brav]

Of course its back again! LOL. 2 days ago, it just got mildly cool, on a high 70s external temp day, after driving, shutting off, sitting in sun, and restarting. Sometimes on a long drive (+30 minutes) it will go back to being cold gradually. I notice that usually when it stops working its also at or above 80F outside, but my external air temp gauge in my cluster always reads +10 to +20 OVER what the real temp is outside.. could this be a related problem? This morning on cold start, AC is ice cold. Temp mid 70s outside

[mmaturo]

The external temp is always wrong and has nothing to do with it though. Audi left the temp sensor from a regular A6 where it originally was...well its too close to our big hot engine. Mine and everyone's is 10 degrees more than the real outside temp after the car warms up.

Its a control unit issue still probably. I described my problem above a bunch of times, but has been fine since last replacement a couple of years ago. It goes brain dead sometimes and does not open the right dampers etc. Although not keeping up on a warm day as you describe you may try getting it recharged, maybe you have just leaked out over time too much.

[Brav]

I did have it recharged prior to this to clear up that issue. There were no apparent leaks. I guess I will hunt for a new control unit (the actual piece with the buttons in the cabin, correct?) Did you buy new or used each time?

[mmaturo]

Yep the actual unit itself. Mine were all under warranty so the last one was over two years ago. I would try to find a new one myself as clearly plenty of old ones did not work. www.genuinevwaudiparts.com This site seems to be the cheapest and best source of parts out there, check with them on cost of new unit. I don't remember it being too much looking at the invoices and it does just pop out.

[Brav]

I looked for 2003 S6, ant it came up as $462 for that bugger. I think I have a source for a free used one, will try that and see what happens. Thanks again for your input.

[mmaturo]

lol...$462 sounds like a BARGAIN. Hell seems everything on the car is $800 normally. Worth trying the free one certainly. You will know immediately if it behaves differently.

If you do go back to buying a new one just email them with your VIN and they will pull up the right RS6 parts for you but that is the amount I remember for it. Hell i was willing to pay it outright when the unit my car came with was messed up/chipped on the buttons by the previous owner.

[Brav]

Ha, I will be fixing the worn off button issue as well . I need to save for new rotors/pads soon, and probably a timing belt soon as well. Have 122k now on the clock.

[mmaturo]

Yep doing the gradual (and seems constant) accumulation of rotors pads now myself...one each paycheck... 280 ea for the rotors on the site above is still the cheapest. EBC reds at $140 on the link in DHall's posts elsewhere here. I also got all the timing belt parts at their prices too.

[Brav]

Resurrecting this old thread.. never found a cure for my problem, but noticed that sometimes I get hot air coming out of lower vents and cooler air coming out of mid?? how can that be possible??

[ben916]

not sure, but you are gonna need it for tomorrow!!!!

[Brav]

Thanks!!!

[Chung]

I have similar issues to what MMaturo describes. It only seems to happen on hot days so it is very difficult to troubleshoot. My econ light actually comes on and the unit won't let the AC engage at hot temps. Since summer has come and gone here I am going to mess with it next year.

I assume you are not getting any codes for the flaps. In my old S4 there was a flap that would go bad causing the routing of air to be all messed up.

[Brav]

Seems like everything points back to the control unit.. I tried a spare used one I got my hands on, but looks like I will be trying a new one.

I will say, the system has never been great. Even when I take it off of Auto mode.. sometimes the fan speed will change on its own anyway! And sometimes she blows out cold air when its already cold inside.. very temperamental.

No fault codes for HVAC ever that I remember.

[Brav]

After driving home from Nevada in 110F temps, she finally gave up the ghost. After stopping after driving for two hours and sitting with engine on for 15 minutes, car got really hot. then ECON light came on, and I couldn't turn it off.. before this happened, when I started her the first time, I got a loud squeal from engine bay which I thought was the car next to me and thought nothing of it. Went away after 3 seconds. I can now get the ECON light off, but I can not hear the compressor engage or dissengage. Just idle change. Duty cycle on the pressure valve shows 100%. Pressure in system shows 9BAR. Maybe its a clutch relay/wiring problem?

I rand VAGCOM and no codes for HVAC..

[4everRS]

My guess is the clutch is shot. I don't think you can get it separate. Need the whole unit.