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Expansion valve possibly stuck open?

joshgray01 on Tue August 04, 2009 8:52 AM User is offlineView users profile

Year: 2002
Make: VW
Model: GTI
Engine Size: 1.8
Refrigerant Type: R134a
Ambient Temp: 93
Pressure Low: 80
Pressure High: 150
Country of Origin: United States

I am working on a my friends 2002 VW GTI A/C. The A/C is not working properly, and it is not producing any cold air at all.

FYI:
The compressor is working (Clutch is engage).
The vent temp is the same temp as the outside air (Hot).
The evaporator does not have any condensation draining from the plenum case.
The low side is reading 80 PSI, and the high side is reading 150 PSI.

The A/C training book that I have is indicating that the expansion valve is most likely stuck opened. So, I wanted to make sure before I tell my friend that he needs to pay for a new expansion valve, and replace the receiver/drier at the same time. If anybody has any suggestions. It will be greatly appreciated! If you need more information, please just ask.

Thanks in advance,

Josh

GM Tech on Tue August 04, 2009 9:49 AM User is offline

That 80 psi is an awfully familiar number- could be just refigerant in your hose- and not reading the real system low side pressure- are you sure gage is connected at port and depressing the valve?

Also, since number one failure mode of any mobile a/c system is lack of cooling due to loss of refrigerant- are you sure you have the proper charge in the system?

Here is a typical scenario- you may want to avoid...

If you change the TXV, you will undoubtedly fix the system--because you will ALSO add back the proper refrigerant amount-when done- and system will cool for awhile at least-- until the leak lets out the refrigerant that you replaced and you get the same failure mode you have now. This is why I always check charge levels first- you can only do this by extracting and weighing the refrigerant.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Tue August 04, 2009 10:37 AM User is offline

I think this car would be like most VWs with a SD7V16 compressor, it's a variable compressor and a lot of them go bad by getting stuck at low displacement. This causes high low side and low high side. You must be sure it is a proper charge before making the diagnosis.

joshgray01 on Tue August 04, 2009 12:12 PM User is offlineView users profile

joshgray01 on Tue August 04, 2009 12:40 PM User is offlineView users profile

Hey GM Tech, I remembered you helped me before about this issue, and I actually made sure this (double checked) particular last time. When I took his readings that there was not any refringent left in the hoses before the readings. FYI: Each time I am through using the manifold gauges. I will release the pressure after the hoses are disconnected. Also, I am making sure that the shader valve is depressed when the coupler is attached. In addition, I have taken his measurements several weeks apart, and they still remain the same readings each time (Low 80 PSI & High 150 PSI). Also, I am not sure if his A/C system has the proper amount refringent in the system. We will have to take it to a shop to have them measure the refrigerant after it is recovered, and I will let you know the amount. So, with this information, what routes would you take to diagnosing this system?


Hey MK378, Do you know where I can get more information on diagnosing compressors?

Thanks in advance,


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