1997 Audi A6 AC compressor stuck - AudiWorld Forums



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1997 Audi A6 AC compressor stuck

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Old 03-14-2017, 01:30 AM   #1
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Default 1997 Audi A6 AC compressor stuck

I was pushing the car hard the other day. I was on a free way and I did max 185km/h for a few seconds. Wasn't violating any laws. During these few high speed seconds, I suddenly heard something weird like something briefly got caught in my fan and the AC stopped cooling off. The air kept blowing, but I noticed that turning on or off the AC did not affect the engine load anymore. I kept driving and spent the rest of the trip without AC.

Back from the trip yesterday, I checked the 10A fuse 5, it was fine. I had the Freon level checked. It was full. The guy who checked the Freon level had a look at the compressor and told me it was stuck. He tried to turn it with his hand and it wouldn't turn.

Is my compressor damaged? Are there any other things to check out? Would excess speed damage the AC compressor?

FYI the car is 20 years old with the original compressor. I've been using it for 3 years and I never had issues with the AC before. Only had to refill the system about 6 months ago.
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Old 03-14-2017, 07:40 PM   #2
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Is the clutch engaging/activating on the compressor? Compressor works like this:

The outer pulley keeps turning with the belt all the time.
When the temp/pressure sensor(s) trigger, there is an internal clutch in compressor -solenoid- that "connects" the compressor's shaft with the main pulley. When compression is no longer required, it is disabled.

So, go through troubleshooting the compressor's clutch solenoid and see if it is activating. I can be done without car running as well with external power supply (disconnect car's wiring before you do this).
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Old 03-14-2017, 11:51 PM   #3
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Is the clutch engaging/activating on the compressor? Compressor works like this:

The outer pulley keeps turning with the belt all the time.
When the temp/pressure sensor(s) trigger, there is an internal clutch in compressor -solenoid- that "connects" the compressor's shaft with the main pulley. When compression is no longer required, it is disabled.

So, go through troubleshooting the compressor's clutch solenoid and see if it is activating. I can be done without car running as well with external power supply (disconnect car's wiring before you do this).
Thanks for replying. It's the clutch the guy tried to turn with his hand with the car off and it wouldn't turn. I guess it is engaged. How do I do the troubleshooting you are talking about? Do I have to dismount the compressor to do this? I have no experience with compressors.
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Old 03-15-2017, 12:21 AM   #4
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I just read an article saying that many systems are equipped with high-pressure cutout switches. These switches open the clutch circuit in the event that pressures become excessive. This function shuts down the compressor and stops the pressure from climbing higher.

I was in 4th gear, at about 6500 rpm at 115 mph when this happened. Could this have caused the pulley to turn so fast that the pressure got too high?

The other day when the guy checked the Freon, he was surprised by how full the system is. Is there anything I could do to cause the compressor clutch do disengage? Maybe let some of the Freon out? Or is there another fuse or relay I should check?
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Old 03-15-2017, 01:54 PM   #5
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I wouldn't let any refrigerant or Freon out. If the system is "charged" to normal levels, you don't need to take any out.

Basically, you need to check/verify the following:

1) Shut off engine and Slip belt off the compressor, disconnect compressor wiring.
2) Try to turn the compressor outer pulley with hand. It should turn freely (or so). If it turns, that means the clutch is NOT engaged.
3) If it is not turning, clutch seized and compressor should be replaced.

If step 2 is OK, then:
a) Check compressor terminals with Voltmeter for resistance/continuity (open could mean solenoid burned out).
b) Lastly, try to supply 12v directly (be sure to use proper wiring / external power supply and maybe a inline 10A fuse - I hope you are familiar with these procedures). You should hear/see the clutch engage. Now try to turn with hand and it should be difficult / won't turn.

If all that checks out, the problem is elsewhere (probably a sensor). Else, the compressor needs to be further checked / replaced.
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Old 03-15-2017, 02:01 PM   #6
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I just read an article saying that many systems are equipped with high-pressure cutout switches. These switches open the clutch circuit in the event that pressures become excessive. This function shuts down the compressor and stops the pressure from climbing higher.

I was in 4th gear, at about 6500 rpm at 115 mph when this happened. Could this have caused the pulley to turn so fast that the pressure got too high?
That's exactly the function of those pressure sensors. They will send a signal or break the signal that will turn off the relay which powers the compressor clutch.

No, I don't think the high rpm caused it. It is possible however if the pressure sensors failed and pressure built up too much.... In that case, I imagine you'd have a different issue of blown seals in the refrigerant lines etc. or plain leak and the level would be low after some time due to leakage.
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Old 03-16-2017, 12:58 AM   #7
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tester123, I appreciate your support on this matter. I will do the troubleshooting you suggested this weekend and report back next week.
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Old 03-20-2017, 04:22 AM   #8
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Clutch is seized and compressor needs to be replaced
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Old 03-20-2017, 03:19 PM   #9
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Clutch is seized and compressor needs to be replaced
That sucks. Try to find a slightly used one and make sure the Refrigerant evacuation/refill is done properly AND with proper OIL!!! Otherwise, you'd be in line for another compressor soon.

If compressor is seized, check for worn belt! It could be cutting the belt due to too much resistance.
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Old 03-21-2017, 03:41 AM   #10
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That sucks. Try to find a slightly used one and make sure the Refrigerant evacuation/refill is done properly AND with proper OIL!!! Otherwise, you'd be in line for another compressor soon.

If compressor is seized, check for worn belt! It could be cutting the belt due to too much resistance.
Alright. Thank you! I think I will keep my C5 as a backup car with very minimum usage for a few months as I'd like to do the timing belt job, the serpentine belt and accessories while the bumper is off. I'm not ready yet.
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