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Old 09-12-2004, 10:17 AM   #1
nebojsa
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Question AC stops working

Hello,
I have a 97 Passat GLX VR6 Wagon. It has about 90,000 miles. A/C has worked perfectly until couple of days ago. I came home with the A/C running, took about 5 mintes to get some stuff and got back in the car. The A/C at that point started blowing the regular air and not the cooled air. I verified that the compressor runs and that it kicks in when you press the A/C button. The strange thing is that when I touch the A/C pipes under the hood, I can see that the pipe going towards the blower motor is very cold. The pipe going back towards the compressor is not cold at all. Are the two pipes supposed to be that different in temperature? What could be causing this?
Also, one more interesting thing is that in the morning when the car runs for the first time, if I turn the A/C on, it will blow cold air for about 1-2 minutes. Then it will gradually switch to the regular warm air.
Does anybody have similar problem with their A/C system?
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Old 09-14-2004, 04:06 PM   #2
boschmann
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Re: AC stops working

You might want to check the vacuum hoses under the hood, particularly the one that goes through the firewall at the heater hoses.
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Old 09-15-2004, 08:36 AM   #3
nebojsa
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Re: AC stops working

Yes, that is what one of my friends suggested. I said to check out that water valve controling the water flow into the heater core. I tried unplugging the connector controling that valve but it didn't make any difference. Do you know if that valve is normaly OPEN or CLOSED when unplugged from power?
I plan on taking off that valve this weekend to see if it is stuck in OPEN position.
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Old 09-15-2004, 09:11 AM   #4
boschmann
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Re: AC stops working

Is this a North American model? You can probably pull enough vacuum by mouth to actuate the vacuum valve to see if it is opening/closing. Rather than go after the heater valve I would concentrate first on the vacuum lines going to the underdash flaps & any vacuum check valves you might have.
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Old 09-15-2004, 05:28 PM   #5
nebojsa
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Re: AC stops working

Yes, it is a North American model. Do you happen to know if this car would have both electrictly controlled heater valve for water and the vacum valve you are talking about? What are the vacuum valves used for in this case? How do I recognize the vacuum valve I need to look at? Is it close to the break fluid container?
Thanks for helping!!!
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Old 09-16-2004, 09:52 AM   #6
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Re: AC stops working

The reason I asked if it was a NA model is because I didn't remember the car to have a vacuum valve for the flow of water into the core. Actually, I don't suspect the heat part of the system to be at fault, nor do I think the A/C has failed. Rather, I feel the problem could be a vacuum line that goes into the passenger compartment right at the two heater hoses, that's the one I was referring to. It provides vacuum for certain air box flaps that can cause your symptoms & it is prone to failure. It's a small (4mm) hose & runs from the firewall to the main vacuum line between the manifold & brake booster. There is also a small (20mm) round check (one-way) valve located in the line. You should only be able to blow through it one way, therefore keep track of which way it was installed.

Last edited by boschmann; 09-18-2004 at 06:24 PM.
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Old 09-18-2004, 01:43 PM   #7
nebojsa
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OK. I have just spent couple of hours looking at the vacuum hoses. I see one vacuum line going into the firewall right with the two water hoses. It apears that this vacuum line controls the air intake in the cabin (i.e. whether outside or inside air will be used). I have a little vacuum pump which I used to test this line. It worked well. Every time I created the vacuum, the air intake changed from outside to re-circulate. It made no impact on the AC at all.
I will try to post some pictures I took so I can show you what I was looking at. See the links below and the little notes.
Also I checked that electric plug going into the water valve. It alsways has 13V on it. It made no diference whether I turned the temperature control to HOT or COLD. BTW, the temperature control works well. It will switch HOT<->COLD. But, still no AC air coming into the cabin and the best I can get is outside temperature.

http://files.automotiveforums.com/ga...cat=500&page=1

http://files.automotiveforums.com/ga...cat=500&page=1

http://files.automotiveforums.com/ga...cat=500&page=1

Last edited by nebojsa; 09-18-2004 at 03:21 PM.
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Old 09-18-2004, 06:32 PM   #8
boschmann
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Re: AC stops working

Well, a quick way to decide if it's a problem with heated water getting in would be to clamp off at least one of the hoses & see if it fixes the problem.
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Old 09-26-2004, 11:12 AM   #9
nebojsa
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Re: AC stops working

Boschmann, just FYI. After I couldn't find the vacuum lines you suggested, and the water hoses looked OK, I took the car to my mechanic. I picked it yesterday fixed and working just fine. My mechanic says that the part controlling the AC intake is not controlled by vacuum. Instead it is controlled by electricity and was somewhere deep inside the dashboard. It cost me $250.00 parts+labor. Ohh well...
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