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 :D. 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??

:doh:

[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.

[mik15]

i am not sure if this does any good, but i always shut off the AC before starting on or shutting off the engine in order to prevent the clutch wear of the AC compressor....

[Benman]

i am not sure if this does any good, but i always shut off the AC before starting on or shutting off the engine in order to prevent the clutch wear of the AC compressor.... I be interested in hearing from our mechanics on board if that would help. :cheers:

[Hy Octane]

When my AC started blowing hot air, they replaced the thermostat that controls the temp and it also fixed my boost problem. Go Figure..

[Brav]

When my AC started blowing hot air, they replaced the thermostat that controls the temp and it also fixed my boost problem. Go Figure..

Heard of this problem before.. can you elaborate which thermostat?

[Hy Octane]

Not really. It was 8 years ago and all I remember is they said it was the thermostat that controls the Climate Control unit..

[4everRS]

I'm sure it was just the temp sending unit. Known to cause all kinds of oddities.

[Brav]

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

Well, you were right. Clutch is shot. Getting a new compressor put in tomorrow.. 660 installeld with all necessary parts and labor. Not too terrible.

I still think I may have an issue with this temp sensor.. I think it may be the temp sensor inside the HVAC vents? it looks very strange, like a miniature metallic pipe organ, if I am thinking of the right part. Blower Motor Regulator?

http://i49.photobucket.com/albums/f282/ckreidel/Audi%20RS6/PN4B0820521blowermotorregulator.jpg

[kday]

That looks more like a heat sink. For a temperature sensor, you want minimal thermal mass. For a heat sink, the reverse. I bet there are some transistors under there that are used to modulate the blower fan speed.

[Brav]

That looks more like a heat sink. For a temperature sensor, you want minimal thermal mass. For a heat sink, the reverse. I bet there are some transistors under there that are used to modulate the blower fan speed.

Yea.. I think it regulates the fan speed. In which case I need it anyway, as mine, even when not on auto, can start creeping up or down 3-4 bars!

[kday]

Mine has no trouble keeping the fan speed constant but can't seem to maintain a steady temperature. Either Audi did a terrible job with the C5 HVAC (which I doubt) or something is broken on mine that doesn't show up on vagcom.

[Chung]

My A/C compressor cost a bajillion dollars installed. That is a great price.

There is also a High Pressure Sensor (G65?) that I had to replace on mine so that the A/C would actually turn on and stay on. This could be completely unrelated since I have no idea what that sensor does.

[Brav]

I know of that switch. Its to protect from over pressure I believe.

[Brav]

Update #2.. another $320 to the bill for parts and labor, since the compressor actually gave out, and sent chunks of metal in the system. there was like no oil in it I guess.. last guy to service it was an idiot apparently. added freon only. So I need new lines, fittings, and a drier/filter. so total repair bill up to about 1k for AC. :/

[Brav]

Update #3... no one has a F***ing dryer in stock. Just some warehouse in TX and 4-5 days to order it via dealership. Tried another Audi unit and the angles wouldnt work, since its so freakin tight in the engine bay...... mechanic is hating me for this job, and for tying up his rack for 5 more days.

Anyone have any idea where I may be able to get one? PN 4B3 820 193 A - seems to be RS6-specific. Or know where I can steal a used one?

http://i49.photobucket.com/albums/f282/ckreidel/Audi%20RS6/photo-20120628-121558.jpg
http://i49.photobucket.com/albums/f282/ckreidel/Audi%20RS6/photo-20120628-121625.jpg

[lswing]

Shokan...

[Brav]

Shokan...

Thanks! :revs:

[kday]

A used dryer ??

[Brav]

OK, new dryer in.. temp is 38 degrees F out of vents now!! BUT.. found out my 300W small radiator fan is toast. Mechanic checked the module which was ok, and continuity test confirmed death of small fan.. which may have lead do death of my old compressor.

Of course, no one has this F-ing part either, and I will have to wait yet another week for parts. And dealer wants 450 for a fan!! Is there any other 300W audi fan I can cross-reference that will work? Anyone happen to know the PN? not showing up in ETKA.

[Shoppinit]

300W fan part number is 4B3 959 455D.

You sure it's the fan and not the control unit, though?

[sheatisdale]

I just developed a similar problem with my AC. I took a 290 mile trip and it worked just fine all the way here. Went out yesterday to buy gasoline before the prices went up and the AC isn't cooling. All I get is air that is ambient or slightly hotter, and I'm near Columbia, SC...so that is some HOT air.

I have good refrigerant pressure and the compressor definately kicks on when I turn the system on, and kicks off and on when I hit the econ button. Today I drove it for a bit and kept switching from AC to econ and back and varying the temperature. At one point it started cooling the air just a bit, but it went back to ambient or slightly hotter just a minute later.

Any ideas?

Thanks,

Shea

[Chung]

I feel for you. My A/C acted up again yesterday. When it gets too hot the A/C will not turn on. Once I was out of the stop and go traffic I ran the car a bit, pulled over at a rest area and turned the car off and on and the A/C worked again.

I am getting intermittent codes for the coolant temp sensor and my second fan control unit. My understanding the control unit for the second fan is built into the fan (probably why it is so spendy)

[Shoppinit]

Nope, the smaller 300W fan has a separate control module. The bigger 600W is the one that has it integrated. And that one is megabucks.

[sheatisdale]

Sorry to hear about your issue. I put the vagcom on mine and I'm not getting any codes from mine. Maybe the 97-100 degree weather is causing the issue for me too.

[sheatisdale]

What should my low-side pressure be at approximately 95-100 degrees outside?

And where is the expansion valve located on our beasts?

Thanks

[Brav]

300W fan part number is 4B3 959 455D.

You sure it's the fan and not the control unit, though?

I'm not but my mechanic is. He tested voltage from control module. Got voltage appropriate for temp. Fan had bad continuity, so bad coil or something. I would imagine thrthing could be rebuilt for way less than 450...

I had bought a control module so if someone needs one let me know.

[Brav]

I just developed a similar problem with my AC. I took a 290 mile trip and it worked just fine all the way here. Went out yesterday to buy gasoline before the prices went up and the AC isn't cooling. All I get is air that is ambient or slightly hotter, and I'm near Columbia, SC...so that is some HOT air.

I have good refrigerant pressure and the compressor definately kicks on when I turn the system on, and kicks off and on when I hit the econ button. Today I drove it for a bit and kept switching from AC to econ and back and varying the temperature. At one point it started cooling the air just a bit, but it went back to ambient or slightly hotter just a minute later.

Any ideas?

Thanks,

Shea

Your and Chungs issues are similar to mine. Same codes too. I had coolant control module 2 codes but wasn't the module in my case. If you have problems with warm air, its probably a dying clutch and/or dying fan. My main fan was coming on a lot. GO GET SYSTEM SERVICED before more damage occurs.. my A/C bill is approaching 2k.. make sure they evacuate the system and even flush it. And properly re add oil. Mine had low oil, and decintegrated.

Also you should have no problem getting cold air with this system in 100 degree air.

[Chung]

I too am at about 2k. Super annoying that it still doesn't work. I can do the coolant temp sensor myself but not sure about the fan. Maybe I need to enlist in some Mark help :). The second fan rarely runs in my case since the code only comes up once and a while.

[Brav]

I bought my module in anticipation of not having to replace it.. but it checks out. I'll send you a PM w info.

[Chung]

Just ordered the fan as well. AutohausAZ has it for $220 if you are in need.

[Brav]

Just ordered the fan as well. AutohausAZ has it for $220 if you are in need.

Perfect thanks!!

[Brav]

Just ordered the fan as well. AutohausAZ has it for $220 if you are in need.

Actually I can't seem to find it on their site. Not even by part number. Can you post a link? Or did you take the last one..

[Chung]

Actually I might had ordered the wrong one. I left off the D at the end.
http://www.autohausaz.com/search/product.aspx?sid=gb54g3qv5qw5us3jeizohv55&pn=W0133-1736450,

[Brav]

Actually I might had ordered the wrong one. I left off the D at the end.
http://www.autohausaz.com/search/product.aspx?sid=gb54g3qv5qw5us3jeizohv55&pn=W0133-1736450,

Yea when I search for cooling fan under 03 RS6, nothing comes up..

I would guess this should be something that someone could rebuild in a day? just need bearings and brushes, no?

[Shoppinit]

Yeah, it's not rocket science, just a DC motor. Question is whether you can get it apart without destroying everything. These things aren't designed to be serviceable.

[sheatisdale]

Well, mine was the compressor. It gave up the ghost. $1800. Ouch.

[Brav]

Got the car back today!! Wow, I am so excited to get it, been nearly a month waiting for misc parts. It sucks to be without it, but when you get it back, especially after driving a 79 Trans Am, its glorious.

All in, 2000 bucks for new compressor, dryer, lines, misc parts, new drive shaft, and labor.. not too bad.

[ben916]

so Chris, is there anything that others can do to perhaps stave off a $2k repair?

[Brav]

so Chris, is there anything that others can do to perhaps stave off a $2k repair?

Not sure, after 150k miles maybe it was due. Mechanic said that dead fan probably over stressed the system, and also last service I got didn't add oil with freon or wvac which probably led to the failure. So the lesson is to check fans and properly service the A/C.

[hahnmgh63]

Yea, it would be better to overfill the A/C oil rather than underfill it. When you bleed or evacuate the system a certain amount of the oil always escapes with the refrigerant so some oil will always need to be added, how much is an unknown so you pretty much have to take a chance but were talking ounces here so too much is better than too little.

[Chung]

To replace the front aux fan does the coolant need to be evacuated? I may try replacing the fan myself if not.

[Brav]

Are you talking about engine coolant or freon? Yes to engine coolant (service position, have to pull bumper way far forward to get access) and no to freon.

[Chung]

yeah, I said coolant and I meant Freon. For the engine coolant, is it ok to just reuse the coolant if you have clean container to put it in. Seems like a waste to drain it perfectly good coolant.

[kday]

Depends on what perfectly good coolant is... if it was flushed and refilled last week, yeah, I'd try to recover it. A partial drain/fill last year? Probably worth adding new.

[Chung]

I had the coolant drained and redone in Feb with my oil cooler pipe replacement.