Year: 1997
Make: Volkswagon
Model: Jetta GL
Engine Size: 1.9L
Refrigerant Type: R134a
Ambient Temp: 76F
Pressure Low: 47
Pressure High: 105
Country of Origin: United States
Placed gauges on this car and raised rpm to 1500; pressures never changed. Added one can of R134a, low side remained while high side barely went up above 110psi. This was refilled only once two years ago. Compressor or txv? No leaks anywhere.
Is the AC not blowing cold at all? Compressor shaft seal will leak over time, not much you can do about that.
I'm not too familiar with automotive AC compressors, but I've been told some are designed with larger clearance volume and smaller valves, which will provide sufficient compression at lower RPMS, but keep head pressures steady on rise of RPMS.
-------------------------
There is no knowledge that is not power
Edited: Sat June 18, 2011 at 11:28 PM by bromodragonfly
Sanden variable compressor. No or little pressure with a full charge. Bad control vale is something to consider.
-------------------------
Found a nice little PDF that gave me a much clearer image of how a variable displacement compressor works. Hopefully it'll be interesting to others too:
http://www.polarbearinc.com/Articles/Variable%20Displacement%20Compressor.pdf
-------------------------
There is no knowledge that is not power
I'm aware of variable displacement compressors. Thanks. On another forum a member posted a final outcome to an issue that was traced to a failed txv but much higher than normal pressures were found on the high side (450psi). The service manual specs for the Jetta calls for 17psi low, 175 high @1500rpm. I'm not familiar with faulty txv's and their characteristics when they fail.
More likely, it's the compressor. Every summer two or three VW owners come here in the same situation. When you know it's fully charged but revving the engine doesn't change the pressure at all, you have a compressor that is refusing to pump.
I haven't seen too many TXV's that have outright failed. But when they do, the most common problem is that they fail to feed enough liquid into the evaporator. This could be due to something foreign blocking the internal port, or sometimes the power element loses its charge, which will result in zero bulb pressure and a closed valve. Both these situations will result in a backup of liquid at the TXV inlet, which will drop the low side pressure. The backup, and the fact that gas coming back to the compressor is superheated more than normal, will result in higher head pressures.
-------------------------
There is no knowledge that is not power
To close this thread I spoke to the owner of the VW and he decided not to invest any more money into this repair. I presented several options but with sound advice from here I relayed this faulty compressor replacement to him. His choice to not proceed any further. Thank you all for your help.
We've updated our forums!
Click here to visit the new forum
Copyright © 2016 Arizona Mobile Air Inc.