Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

98 VW AC problem

carMILLIONZ on Thu June 17, 2010 7:09 PM User is offlineView users profile

Year: 1998
Make: Volkswagen
Model: Jetta
Engine Size: 2.0
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 60
Pressure High: 300
Country of Origin: United States

My boss's 98 VW air conditioning just stopped working a few days ago. it worked one day, and after the weekend when she got in, it didn't cool. I checked it and found 60 low, 300 high. The compressor seems to be working properly, although sometimes the pressures fluctuate up and down 20psi or so. Someone told me the compressor is variable displacement and that can cause that?

The AC is not cooling at all. Both electric fans are working fine. The high side line going into the condenser is hot, leaving the condenser is ambient or a few degrees above. The TXV is just slightly cooler than ambient, but not by much. The low side line leaving the evaporator is ambient temp. not at all cool. It doesn't get cold or sweat. If you add just a tiny bit of freon (an ounce or two, maybe), pressures spike to 400+ and the compressor shuts off.

I don't have the AC skills to troubleshoot this. I was going to start throwing parts at it, by starting with the simple stuff. a TXV and the accumulator/dryer. Both are easy to replace and fairly inexpensive. If anyone has any advice, I'll gladly listen.

I repair airport preconditioned air units that cool aircraft, so I have gauges, vacuum pump, and a little bit of knowhow. mostly those units never have a problem except for leaks, blown compressors and stuff like that. they are big, 30 tons running 134a. This car just has me stumped.

Thanks for your help.. I really appreciate it!

bohica2xo on Thu June 17, 2010 9:16 PM User is offline

Just be glad your big units don't have variable displacement compressors...

The 60 psi on the low side is your first clue. Way too high to provide cool air. The compressor should be trying to hold the low side around 33 psi by changing displacement.

The cool (near ambient) condensor discharge and not so cold TXV make the TVX suspect in this case. The added ounce of refrigerant spiking the high side would point the same direction.

Does the low side pressure drop when you turn the cabin fan to the lowest speed?

I would recover the system & inspect the TXV. Given the age of the vehicle, the drier should be replaced. If you are going to throw parts at it, the TXV might solve the issue - depends on what the old one looks / acts like.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

carMILLIONZ on Fri June 18, 2010 1:04 PM User is offlineView users profile

I replaced the TXV, pulled a vacuum and recharged the unit to the proper amount by weight. I now get 65psi low, 125 high. I'm guessing its the compressor. but thats just a guess. any thoughts?

bohica2xo on Fri June 18, 2010 2:05 PM User is offline

Looks like it. Now it can't pass 125psi, with a functioning TXV.

Variable displacement pumps can be a PITA for diagnostics, because other failed elements in the system can make them behave in different ways. The VW is known for issues like this, some techs tap on the compressor to see if the control valve moves... but if it stuck once it will do it again.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.