Hi everyone,

I recently traveled to a hotter area than usual where we got 105F. Our AC was barely cooling. I assume I need to add R134a freon. However, I noticed that the AC Compressor clutch always seems to be rotating regardless of whether I turn on or turn off the AC. I noticed if I turned on the AC the rpm engine slightly increased and if turned off the engine rpm slightly decreased. I think it is normal. However, I never see the external ring (clutch) of the AC compressor stop rotating. In addition, I had a chance to check the same with GL450, 2007, and BMW X3, 2014. Both vehicles behave the same. I am wondering if I missing anything or if something is wrong with all the cars.

Finally, what are the R134a pressure levels for low and high lines are good for Mercedes GL550 2014? Any help is highly appreciated!

 

External ring is always rotating on AC compressor regarding of the vehicle type. That is the reason it called clutch, you need to pay attention if central part attached to axis compressor turning or not. Either way that is not a reason for your low AC performance. There is an electronic valve on the side of compressor which bypass freon pressure from high pressure side to low pressure side for variable performance. I believe it cost about 25 bucks for made in China and couple hours of work to replace it. With a time it usually either got clogged with debris or start leaking leading to poor HVAC performance.

 

I did Xentry diagnosis. It does not give me any errors. Do you know if this electronic valve is not working, should I get an error in Xentry? Thank you!

 

Xentry or anything or anyone else don't test these valves.