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Discussion Starter #1
About a year ago my accessory fan died. This was confirmed by putting direct power to the fan motor with no results. Anyways....the AC would blow cold as long as the vehicle was in motion, I assume this is from air passing over the condensor from the car moving. Over the weekend I developed an oil pressure problem and put the car in the shop for a new oil pump. While they had the car in service position I figured now would be a good time to have that fan replaced. Well i picked the car up Monday night, now I have NO cold air, moving or standing still.

I talked with the ship and they said they didn't touch the AC system itself, just the fan. I've checked the interal fuse and its fine. Tomorrow ill check and make sure the ac clutch is engaging as it should as well as check the system pressure.

Anything else I should check?

It seems a bit of a coincidence that this happened at the same time it was in the shop. When moving into service position could something have been unplugged, pulled loose, or damaged?

General thoughts or suggestions please.

I trust this shop as they have saved me money in the past with their honesty.
 

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Tomorrow ill check and make sure the ac clutch is engaging as it should as well as check the system pressure.

Anything else I should check?
Your plan is the logical first step. This is where VAG-COM could help; you can run the electric fan and test the compressor clutch, plus check for electrical faults. As you probably know, when you turn on AC, the clutch should engage, and the evaporator pipe (larger aluminum tube next to battery) should feel cold fairly quickly. If the clutch doesn't engage, check the high-pressure switch connector, which I believe is on or near the condenser. If that's OK, you could try disconnecting the electrical connector to the low-pressure switch and check it for continuity. If open circuit, try bridging the harness connector to see if the compressor runs. If so, either the pressure is too low, or the switch is defective.
 

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Discussion Starter #4
No noticable clicking when turning on and off. The auxiliary fan comes on but that's it. The lines do not change.temperature. when I plug my ac gauges in they max out. I need to find out where the high and low pressure switches are
 

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Discussion Starter #5
OK, here is where I'm at. I found the high/low pressure switch behind the lower right fog grille. The switch has been removed and the harness has been jumpered to check working order of the system.

When I jumper wires 1 and 2 I get NO RESULTS.

When I jumper wires 3 and 4 the accessory fan turns on faster.

This leads me to believe something other than the pressure switch is not working.

Haynes manual says to check under hood fuses... where are those? I checked the in cab fuses and they are fine.

Pressure on the AC system with the car warm is...MAXED OUT.

Whats next?

HELP ME OUT PLEASE!
 

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Discussion Starter #6
I checked relay 384. I am not getting battery voltage to pin 9. This leads me to believe its the pressure switch or low on freon. I'll be getting some freon and a new pressure switch tomorrow unless someone can offer some other suggestion.
 

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Remember, you must first evacuate the system before replacing any pressure switch. Care must be taken to assure no compressor oil is lost while evacuating.
 

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Discussion Starter #9
The system does NOT need to be evacuated first. There is.a schreider valve where the pressure switch screws in
 

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The system does NOT need to be evacuated first. There is.a schreider valve where the pressure switch screws in
That's correct. But I just took a quick look for the LP switch on my Wife's '99 1.8T, and it wasn't where it is on my '96 A4, by the pollen filter. However, it has to be on the return line back to the compressor.
 

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Discussion Starter #11
The pressure switch is located behind the passenger side dog light grill. It's hidden up.high but its reachable and removable from the opening.
 

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Discussion Starter #12
Returned to the shop just now. Spoke with the tech who did the repair/install. We walked through each step and discovered that the ac clutch power wire somehow got dislodged. One simple plug in connector by the drivers.side headlight. What a nightmare. They apologized profusely. Still a happy customer abs and have AC
 
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