Automotive Air Conditioning Information Forum (Archives)

AllenIN on Tue June 21, 2011 7:37 PM

Year: 2002
Make: Volkswagon
Model: Beetle TurboS
Engine Size: 1.8
Refrigerant Type: 134a
Ambient Temp: 85F
Pressure Low: 35-125
Pressure High: unknown
Country of Origin: Mexico

Hello:

I'm having trouble with my wifes VW Beetle TurboS A/C.

I have been unable to find the high side, so I'll tell you what I know and hope that you might have some idea what the problem is.

When the clutch kicks in, the low side drops to 30-35psi and when it kicks out, it rises to 125psi in about 10 minutes, at which time it then kicks in again and drops quickly to 30-35psi again.

I also noted that when the clutch kicks in, both of the radiator fans run as well and then shutoff when the clutch kicks off.

I noted cooling while the clutch is engaged which quickly dissipates when it kicks out.

I tried giving it a top up of freon, but it refused to take it.


Thanks for any help you can offer.

Allen

bromodragonfly on Tue June 21, 2011 9:43 PM

Hard to tell what's happening without a high side pressure reading. Sometimes it helps to go to the dealership and ask for a diagram of the AC system, so you have a good idea of what components your car contains. If you're gonna look under the hood, the high side fitting will be anywhere from the discharge port of the compressor, to the metering device (most likely TXV or orifice).

A cutout on the low side of 30-35 psi seems a bit high, and the fact that it isn't cutting back in until 125psi kind of signals that the system isn't normally cycling on low pressure.

Is the cooling during the phase where the compressor significant? Does the compressor cut out in a matter of seconds after engaging?

I would say the compressor is cutting out on high pressure. Or there is a mechanical problem with the clutch staying engaged... but it would be more than coincidental if it was disengaging every time suction pressure hit 30, and engaged again after 10 minutes each time. I'm don't consider myself strong on automotive mechanics, but someone else here will definitely know what to look for.

High pressure could be caused by a crapload of different things. I'd say if the compressor changes the suction pressure from 125 to 30 quickly, it is moving refrigerant. A quick cutout sounds like a large restriction somewhere on the high side. Ten minutes to equalize pressures also seems kind of long, but I don't know enough about your particular system to know if this could be normal or not.

Has anyone serviced/charged the system recently? When the car is sitting around and the engine is cold, take note of the ambient temperature and take a reading of the static pressure. Try to find that high side fitting.

-------------------------
There is no knowledge that is not power

AllenIN on Wed June 22, 2011 10:00 PM

Thank you for taking the time to reply.

Later, after posting my question, I continued searching for an answer and found the VW forum. It seems that there is a very usual problem with my model of VW.

It has to do with the fuses which sit on top of the battery. There is a connection box with 3 30A fuses that sits on top of the battery. The fuse to the left of the 3 fuses in a row was starting to overheat which caused some melting and then caused corrosion of the metal on the prongs of the fuse. This made the fuse loose contact and was causing the intermittent cutting out of the clutch.

I pulled the fuse and wire brushed it and then flipped it around and plugged it back in and everything worked as is should. When I turned on the AC, it continued to cycle until I turned it off.

If the melting and corrosion gets too bad, the connection box with fuses can be replaced. Parts are from $80 to $110, but far cheaper than a new compressor.

Thanks again for trying to solve my problem. I sure appreciate the effort.

Allen

bromodragonfly on Wed June 22, 2011 10:27 PM

Glad you got it solved I wouldn't have figured that one out before Christmas

-------------------------
There is no knowledge that is not power