AC Problems - Help
Thread Starter
Audiworld Junior Member
Joined: Jun 2004
Posts: 44
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AC Problems - Help
My AC stopped working, now it blows ambient (hot) air.
Info on my car: 97 audi a4 Q 2.8L 12v , manual trans, with 172k.
The AC was working fine (cold quick and stayed cold) up until the other day. I parked my car last week one night after my commute home with the AC working fine and blowing cold air, but when restarting the car an hour later the AC would only blow ambient air.
My RPM blips when turning off and on the AC while idling so I believe the compressor is working. I have had the refrigerant pressure checked and it was fine, had it replaced just to be safe, and still AC is only blowing hot air.
Any suggestions on what else this could be and how to diagnose it? I will not be making any big repairs to the AC but if it could be a switch or sensor somewhere I would love to check them.
Thanks for your help in advance.
Robb
Info on my car: 97 audi a4 Q 2.8L 12v , manual trans, with 172k.
The AC was working fine (cold quick and stayed cold) up until the other day. I parked my car last week one night after my commute home with the AC working fine and blowing cold air, but when restarting the car an hour later the AC would only blow ambient air.
My RPM blips when turning off and on the AC while idling so I believe the compressor is working. I have had the refrigerant pressure checked and it was fine, had it replaced just to be safe, and still AC is only blowing hot air.
Any suggestions on what else this could be and how to diagnose it? I will not be making any big repairs to the AC but if it could be a switch or sensor somewhere I would love to check them.
Thanks for your help in advance.
Robb
AudiWorld Member
Joined: Mar 2000
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From: Evanston, IL
Do you have access to a VAG-COM scanner? My guess is that the temperature flap solenoid has gone flaky or failed, which will show up immediatley with a scan of the HVAC head unit. Note that if you don't fix this, you may not have heat in the winter, which is why I fixed mine!
AudiWorld Super User
Joined: Jun 2008
Posts: 2,284
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From: Fallbrook, CA
Watch the front of the compressor, you should see the entire pully assembly turning when the AC is on. Next, is the larger of the aluminum tubes near the cabin filter housing cold to the touch? If it's yes to both, then the interior flaps are likely the problem.
you said the refrigerant was changed to be sure; did a shop do that and if so what did they suggest?
you said the refrigerant was changed to be sure; did a shop do that and if so what did they suggest?
Thread Starter
Audiworld Junior Member
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Thanks for the two suggestions. I do have Vag-Com but it is only the freeware version. I scanned the HVAC (module 08 I think it was) I had no codes that were relevant to the AC. I had one code for an intermittent ignition switch (cleared and has not returned) but nothing else, I know this is a recall item but I haven't gotten around to having it fixed. I also tested if I had heat, I can blow very hot air when the temp is turned up all the way.
I haven't had a chance to closely inspect the front of the compressor pulley with the AC on but will check this soon. The larger of the two tubes near the cabin filter does not get cold.
I had the fluid replaced at a Jiffy-Lube type place and when that didn't work they were not to helpful other than saying it could be a evaporator or condenser problem...
I find the situation odd in the fact that it was working excellently when I parked the car and then one hour later would not work at all. It makes me feel like a switch or a sensor just went since it was so sudden and is not leaking refrigerant.
Another note about my car is that I do run oil temps around 225F but the coolant temp stays stays straight up and down after reaching operating temp.
Thanks for the suggestions.
Robb
I haven't had a chance to closely inspect the front of the compressor pulley with the AC on but will check this soon. The larger of the two tubes near the cabin filter does not get cold.
I had the fluid replaced at a Jiffy-Lube type place and when that didn't work they were not to helpful other than saying it could be a evaporator or condenser problem...
I find the situation odd in the fact that it was working excellently when I parked the car and then one hour later would not work at all. It makes me feel like a switch or a sensor just went since it was so sudden and is not leaking refrigerant.
Another note about my car is that I do run oil temps around 225F but the coolant temp stays stays straight up and down after reaching operating temp.
Thanks for the suggestions.
Robb
Jim Robertson
Joined: Aug 2005
Posts: 113
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From: Stouffville, Ontario
Read your descriptions. Your system likely has lost pressure. The refridgerant may have tracer colour which would show leaks. You could find it with a black light if it was tracer fluid.It's a flourecent dye.
The compressor won't engage without fluid. Look for leaks in the seams of the condensor rad, the one at the front of coolant rad.
Failing that it could be the compressor or the low pressure switch. It's the one near the cabin filter.
Most likely a leak if your pipes don't get cold.Based on the vintage of your A4, seam leaks are common. Look for the same kind of leaks in your rad too while your at it.
The compressor won't engage without fluid. Look for leaks in the seams of the condensor rad, the one at the front of coolant rad.
Failing that it could be the compressor or the low pressure switch. It's the one near the cabin filter.
Most likely a leak if your pipes don't get cold.Based on the vintage of your A4, seam leaks are common. Look for the same kind of leaks in your rad too while your at it.
Thread Starter
Audiworld Junior Member
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Thanks for the suggestion, I don't think it is a pressure leak because I am not loosing any refrigerant (system still at at the right pressure). Is there any way to check the low pressure switch function? Thanks!
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Thanks for the suggestion, I don't think it is a pressure leak because I am not loosing any refrigerant (system still at at the right pressure). Is there any way to check the low pressure switch function? Thanks!<center><object width="1" height="1">
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AudiWorld Super User
Joined: Jun 2008
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From: Fallbrook, CA
When you unscrew the pressure switch, it should click (assuming that there is enough pressure). It will click again when it is threaded back on. Use a meter to check: should have continuity across the contacts in the first case, and none in the second case.
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Joe Kucinski
AudiWorld Member
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From: Evanston, IL
Easier way: bypass the low pressure switch
Unplug the low pressure switch connector. Insert a bent paper clip across the leads in the connector momentarily, see if the compressor turns on. DO NOT LEAVE IT THIS WAY!!!
But first, check to see if the compressor is turning on - I don't recall or see if you have done that step yet.
But first, check to see if the compressor is turning on - I don't recall or see if you have done that step yet.