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Jetta wagon Evaporator freeze up

Poormech on Fri July 29, 2011 1:59 PM User is offline

Year: 2001
Make: Volkswagen
Model: Jetta
Engine Size: 2.0
Refrigerant Type: 134a
Ambient Temp: 95
Pressure Low: 19-25
Pressure High: 225
Country of Origin: United States

I'm having a slight problem with a Jetta wagon and the evaporator freezing up after about 40 mins of driving. The air out the vents will slowly diminish. Previously the system had died and I replaced the Compressor, condenser, Dryer, Expansion Valve, All seals, flushed all lines and evaporator with a/c flush and purged until dry. I put the proper amount of oil in the system. Using a recovery machine I vacuumed the system for an hour then charged into a vacuum. The system is quiet and cools a little too cool usually at about 33 degrees out of the vents on a 90 degree day. Then after about forty minutes the evaporator freezes. I went and bought a factory expansion valve and replaced it using the same procedures, only to have the same problem. Turning on the heat or parking the car (at the store) will resume full air coming out the vents when turning the system back on. The only switch I'm aware of is the high/low switch right before the expansion valve. Could this be the problem? My understanding is that this switch is for low freon/hi pressure switch. This system does not have a digital control panel either. Thanks in advance for your help, Dave

JJM on Fri July 29, 2011 11:54 PM User is offline

Probably another bad Sanden SD7V16 control valve and the compressor is not destroking. We see this problem a lot, except the opposite problem - compressor is stuck destroking.

Where was the compressor sourced from? That usually helps pinpoint the issue.

The good news is likely just the control valve is bad (common problem). The bad news is the system needs to be discharged and the compressor disassembled to get at it, which takes some specialized tools.

Only other alternative or workaround might be to install a temperature or pressure switch, allowing the compressor to "cycle".


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mk378 on Sat July 30, 2011 11:33 AM User is offline

Like JJM said, the evaporator temperature is controlled by the compressor being designed with variable displacement so it will no pump the low side too low. It doesn't cycle during normal operation, the switch is only for safety purposes and will be closed at all times normally.

Poormech on Sun July 31, 2011 3:14 PM User is offline

Thanks for the information. You guys are the best! Replacement shouldn't be a problem since the company I bought it from here in Ga. said it has a year warrantee and since I have a recycle machine, the job should be a breeze. This place is a major distributor for the whole state so they deal pretty much on the level. Thanks again for your help and I'll let you know the results after the change.

Edited: Sun July 31, 2011 at 3:24 PM by Poormech

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