A/C freeze-up compressor not cycling - summer coming, help!
06-15-2005, 01:38 PM
#1
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A/C freeze-up compressor not cycling - summer coming, help!
After 30-40 minutes of dirving my A/C freezes the lines and very little cool air gets through to the interior of the car, although the fan can clearly be heard still working. I speculate that the compressor is working all the time rather than cycling on and off. What part has failed?
Any help would be appreciated.
Any help would be appreciated.
06-15-2005, 01:50 PM
#2
Are the "lines" freezing up, or are the air side coils of the evaporator freezing up?
From your description of "very little cool air gets through to the interior of the car", that's what it sounds like.
This is commonly caused by a low refrigerant charge. You'll probably need to recharge the system.
This is commonly caused by a low refrigerant charge. You'll probably need to recharge the system.
06-15-2005, 01:52 PM
#3
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The compressor normally runs all the time
The clutch stays energized unless you are in a high or pressure situation and then it trips it off line.
What is freezing up? The evaporator? How do you know this?
Is the fan blowing air into the cabin?
What is freezing up? The evaporator? How do you know this?
Is the fan blowing air into the cabin?
06-15-2005, 02:18 PM
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Re: The compressor normally runs all the time
After an hour of driving I pulled over and popped the hood. The A/C line was totally covered with frost from the firewall to the jar shaped thing (covered in frost)attached to the fender and also just as frosty from there to the engine. I could feel and hear the fan blowing under the screen at the center of the firewall.
VERY little (almost none) airflow was entering the cabin of the vehicle through the vents, but what came through was cold. hitting + until all bars lit increased the fan noise but did little else.
Hitting - until system off turns off the system, and after 15 or so minutes, A/C acts normal for about 30- 40 minutes and the cycle repeats.
VERY little (almost none) airflow was entering the cabin of the vehicle through the vents, but what came through was cold. hitting + until all bars lit increased the fan noise but did little else.
Hitting - until system off turns off the system, and after 15 or so minutes, A/C acts normal for about 30- 40 minutes and the cycle repeats.
06-15-2005, 02:20 PM
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Re: Are the "lines" freezing up, or are the air side coils of the evaporator freezing up?
Where are the air side coils?
I (stating the obvious)know very little about these systems...
I (stating the obvious)know very little about these systems...
06-15-2005, 02:51 PM
#6
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Your Problem: Interior Cabin Ventilation Path Blocked
The reason why everything is freezing up is because there is little to no load on the system.
Why is that? Because you ventilation dampers are not working correctly.
I had almost an exact problem when I purchased my car. The damper (thing that opens/closes to allow air flow and throttle it) that allowed outside air into the car was wacko (kinda like some women I know) and wasn't doing what the HVAC head unit was telling it to do.
You can easily see if the dampers are working properly with vag-com under measuring blocks. I'll assume you don't have this tool.
To troubleshoot, drive around when there is little to no air flow coming out of the vents, then put the system into "RECIRC", that little button with the arrow at the end of the semi circle.
This will realign the outside air damper to close (which it basically already is) and open a recirc path from the cabin back across the evaporator (the coil that has the cold freon in it cooling the cabin).
If this works, then it's the damper I discussed.
If it doesn't, either bring it to the stealer and have them check it, or just use measruing blocks under vag-com and you'll see a target versus actual position being off more than 5 points on another damper.
Once you find the bad one, it needs to be replaced, about a $120 part.
Now back to those wacko women......
Why is that? Because you ventilation dampers are not working correctly.
I had almost an exact problem when I purchased my car. The damper (thing that opens/closes to allow air flow and throttle it) that allowed outside air into the car was wacko (kinda like some women I know) and wasn't doing what the HVAC head unit was telling it to do.
You can easily see if the dampers are working properly with vag-com under measuring blocks. I'll assume you don't have this tool.
To troubleshoot, drive around when there is little to no air flow coming out of the vents, then put the system into "RECIRC", that little button with the arrow at the end of the semi circle.
This will realign the outside air damper to close (which it basically already is) and open a recirc path from the cabin back across the evaporator (the coil that has the cold freon in it cooling the cabin).
If this works, then it's the damper I discussed.
If it doesn't, either bring it to the stealer and have them check it, or just use measruing blocks under vag-com and you'll see a target versus actual position being off more than 5 points on another damper.
Once you find the bad one, it needs to be replaced, about a $120 part.
Now back to those wacko women......
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06-15-2005, 06:06 PM
#8
Then why doesn't my AC freeze up after an hour at the lowest fan speed?
Your right, the A8 compressor doesn't cycle. Surprised me to find that out. But doesn't it seem that with the AC programmed to use very low fan speeds once the the car's cool inside that everybody's evaporator would be icing over if it requires a minimum airflow to stay defrosted? And wouldn't it happen faster when it's just above freezing outside, when some people run AC for the dehumidification? I'd guess that 1999audia8's restricted airflow is caused by the icing, not the other way around, so the next question is how does an AC evaporator get too cold? Wrong charge? Bad metering orifice? Sometimes I wish I had that problem.
Also, sometimes bad flap motors are actually caused by bad electrical connections at the motor plug. Mine had lost its + connection to the feedback potentiometer. It was stuck mostly shut and giving the usual code. The clue was that the measured position was very low, about 4, well below the learned limit. Unplugging it and plugging it in returned it to normal, and some Stabilant will hopefully keep it happy. Been working for about a month since that happened.
Tom
Also, sometimes bad flap motors are actually caused by bad electrical connections at the motor plug. Mine had lost its + connection to the feedback potentiometer. It was stuck mostly shut and giving the usual code. The clue was that the measured position was very low, about 4, well below the learned limit. Unplugging it and plugging it in returned it to normal, and some Stabilant will hopefully keep it happy. Been working for about a month since that happened.
Tom
06-15-2005, 07:12 PM
#9
Just like any other AC if the radiator on the front is clogged, dusty, full of leaves.....
it is not able to discharge heat. It happens to any AC system in dusty environment.