Quick question regarding the AC system. If it’s below freezing, it seems the car’s AC doesn’t kick in when the HVAC is set to “Lo”. Understandably, this is probably due to the fact that it doesn’t need to kick in as the air outside is cold enough. So my question is, is there a way to force the AC to kick in even when it’s below freezing outside? Does the front windshield defrost use the AC system, regardless of the outside temperature to remove humidity?
Thanks.
Interesting
AFAIK the system is hardwired not to turn on the AC if the ambient temp is below +5*C. So any bypassing of this would involved fooling the ambient temp sensor that it is above that. Or maybe try disconnecting the sensor?
Ok, thanks for the update. I’ll just wait till Wednesday when it’s supposed to be 11c.
I was always told that having the A/C compressor on in cold temps can damage it.
However, our compressors are different in that they are variable vane. The compressor is almost always on when the heat is on to remove humidity from the air, it’s just not on full stint. There is a block in vag-com where you can see the output percentage of the compressor. If you hit the ECON light at idle you will notice the engine free up some from the compressor load going away. Also, whenever you have the defroster on in the front, the compressor is cranked up so it’s blowing completely dry air at your ‘wet’ windows
x2
where did you hear this from? Is this specific to the variable vane compressors? Never heard of this
Well, here’s my situation. My econ light is almost always on (but not always, about 90% of the time). Yesterday, it wasn’t on so I turned the temp down to lo and cold air was pumping out of the vents but I didn’t see any change in my rpms (usually, when it kicks in, you see a small blip in the idle rpms from the compressor kicking in).
However, it was -2c and I’m therefore wondering if it was just too cold outside. I’ll try putting the defrost on and see what happens and scan the HVAC for codes. Any idea where I can see the compressor’s output percentage with VCDS?
I’d suspect the controls for the compressor relate desired temp to inlet temp and manipulates the compressor vanes accordingly… if inlet is below desired it shouldnt bother adjusting the vanes
Can you manually turn the ECON mode on and off? Or does it come on on its own? If it does that means there is a problem with the system. Scan it and see if there are any codes should be step 1.
Folk wisdom. I was always told that by old people. Guess it’s an old wife’s tale?
may be an issue on a super old a/c, anything with a properly working thermostat should be fine… dial back amperage until outlet temp is higher than desired temp
Well that’s the problem. There is something wrong with the system. I just don’t know which part and I was therefore trying to single out the compressor. I have a small window of opportunity to buy a heavily discounted compressor but I don’t want to buy it unless I need it. However, I don’t want to miss the opportunity to buy it either in case it is the compressor. I was therefore hoping someone could help me out re figuring out if it’s the compressor or one of the other many factors within the system.
I would eliminate all the other possible causes before you blame the compressor. I see your supercharged. Don’t some A/C lines have to be moved around to fit it? Is it possible you’re just low on freon? Even being just slightly low can cause the system to not work properly and cause the compressor to not kick on. We do ALOT of A/C jobs at my shop by far the most common problem is low freon. Now if the system is low you might have other issues but its a good place to start after you scan for HVAC codes.
Ok, good to know. I’ll scan the codes and post whatever I find here.
Ok, so I scanned the “Auto HVAC” for fault codes and this code came up. I then cleared it and it came back right away. Cleared it again, came back right away again.
Tuesday,07,March,2012,16:46:42:26365
VCDS Version: Release 805.1
Address 08: Auto HVAC
Control Module Part Number: 8E0 820 043 AM
Component and/or Version: A4 Klimaautomat 2831
Software Coding: 00000
Work Shop Code: WSC 00000
1 Fault Found
00819 - High Pressure Sensor (G65)
07-00 - Signal too Low
I also took a screenshot showing various parameters here: http://www.gauntlet.net/audi/ac_screenshot.jpg
http://www.gauntlet.net/audi/ac_screenshot.jpg
The High Pressure sensor is at 11% and the range is 12% so that makes sense that it’s causing a fault code although I don’t know what it all means.
The compressor’s torque was 0 telling me it wasn’t running but that may because it was cold out. Not sure if that’s normal or not. I tried both setting the temp to LO as well as the defrost. I guess I’ll try again tomorrow when it’s warmer out.
Any thoughts?
I have no idea, but damn your car has some unique issues at the moment
Tell me about it. It’s driving me nuts. Between the bogging that no one is completely sure how to resolve, the clutch issue where everyone is suggesting changing the slave cylinder but it’s been shown by another member that it didn’t fix the problem and now this AC issue, it’s a pain. Now, the AC issue is the least of my concerns at the moment as it’s still cold here but I’m scared it might be the compressor (or some other high cost repair). The clutch is stopping me from properly enjoying the car as I can’t drive it hard and I don’t want to simply throw parts at it and the bogging, well, I’m waiting to hear back from Carlos to see if he’s discovered anything. JHM says they’re working on an updated B7 tune but there’s no ETA. I’d like to have all of this resolved before spring but it’s not looking great right now. Sigh…
As for the AC it’s 15 deg out and my compressor kicked in so get out this afternoon if you can.
Just about to. I’m on my laptop at Starbucks about to cross the street and run some tests.
Update: Ok, well, I’ve confirmed the AC is NOT working and there’s no change in the readings. I’ll take it to the mechanic and let them figure it out I guess.
With any A/C issues, it’s best to take it to Audi and pay the $155 or so to have them do the hard part of finding what is going wrong. There’s so many sensors and relays that can make it look like a bad compressor. My compressor works but only when the temp is <75. Go figure.
