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Cools well at Idle only

harryakc on Thu June 10, 2010 8:49 AM User is offlineView users profile

Year: 2002
Make: Volkswagon
Model: Jetta
Engine Size: 2.0L
Refrigerant Type: R134
Ambient Temp: 85F
Pressure Low: 113
Pressure High: 175-200
Country of Origin: United States

Have a problem with cooling.
Problem started with low side 113 and high side 200 but increased dramatically to over 300. evaporator temp was 75F at this time. All of this is with car in park and at idle speed. Found a bad condenser fan and replaced.
Now, I get evaporator temp of 45F at idle and low side of 113 and high side of 175-200. When RPM's are increased to 2500 rpm or so(car is in park in garage) evaporator temp goes back up to 75F. Low side stays at 113 and high side is still now at 175 to 200. Compressor is always running and never cycles off.
Car always stays at 45F until I bring up the rpms 1st time. Then is seems to take a while for the evaporator temp to return back to 45F. I may have even had to turn the car off and on and turn AC back on the get evaporator temp back to 45F, but I have to confirm this since I'm not sure. Any ideas would be greatly appreciated.

JACK ADAMS on Thu June 10, 2010 11:22 AM User is offline

Be sure that the gauges are closed and if they are then you will have either a bad TXV or a compressor on its way out.

harryakc on Thu June 10, 2010 12:10 PM User is offlineView users profile

Yes, gauges are closed. Could air or moisture cause any of this? Also is this vehicle make and model designed to have compressor run all the time?

ice-n-tropics on Thu June 10, 2010 1:05 PM User is offline

VW uses Sanden SD7V16 variable displacement, variable stroke, compressor which normally does not cycle clutch while in A/C mode.
You do not have indications of moisture in A/C
Your low side suction pressure gage is surely out of calibration because 45 degree louver relates to under 45 psi
If suction pressure remains the same between idle and 2500 rpm then temp should be the same if high side is reasonable
Higher rpm can increase engine coolant pressure and possibly cause malfunction of coolant shut off valve or cause change in signal which positions blend air door
Block heater hose coolant flow by adding cheap manual shut off valve to check if problem is reheat of chilled air at higher rpm

Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy. How To Air Condition Your Hot Rod

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