Have VW Passat CC with cooling stopped working. I had NT530 on hand at the time. I hadn’t used NT530 to deal with this problem before. I tried it and thanked it for its usefulness.
Hook hooked up Foxwell scanner and noted 10 bar refrigerant pressure, several amps of compressor current when AC switched on, but only small change in compressor load and engine load. Noted that main engine fans only kicked in when engine temp was high enough (couldn’t find that this is wrong).
Image 1: Foxwell NT510 Elite VW scanner (same as Foxwell NT530)
The following demonstrates how to select this function in the device:
I found this related to the refrigerant pressure sensor:
“Switches the coolant fan to the next higher level when the pressure in the refrigerant circuit increases (approximately 16 bar (232 psi)).”
Finally worked out!
Replaced the compressor today with a Nissens and all is good again. The old pig has no noticeable resistance when you turn it by hand – probably a bad reed valve.
Credits to @ Hirnbeiss