stuck EC is usually indication that your refrigerant too low. start there imo

 

The always-on red light indicates that the computer has turned the compressor off because of a problem. It might be low refrigerant, or might be some other problem. In my case, I think that the compressor momentarily seized, destroying the serpentine belt and top idler pulley...

You might be able to query the HVAC diagnostic system on the Command screen - if not, you will the STAR/DAS system to determine the problem.

 

Hi Wally. Sorry for the confusion, the steps a) - e) are things I've already done and their results. I checked the refrigerant - c) above, and AFAIK you can't add refrigerant when the low side is ~90 PSI, so I need to get the compressor turning to add refrigerant - Do any techs know wether the AAC pushbutton unit actually controls the compressor clutch? As you can see the first code I read, "KLA A 1000" means : "AAC Pushbutton Unit (N22) is defective" the 2nd code, "KLA V 1241" means low refrigerant, but 90psi doesn't seem low enough (does it?) to cause the code unless the sensor is on the high side. I guess I'll consult the AAC schematics...

 

90 psi with the compressor NOT running is low (when running will go to 45 - 80 psi on the suction side)

You need to reset the control with DAS in order to charge it, or discharge it and then liquid fill with correct amount. Then you still have to reset, as the control has gone into fail-safe to protect the compressor.

BTW: a lot of W220 don't have a compressor clutch, so regular shops can't do the reset.

Good luck!

 

Thanks for the reply. I don't currently have DAS, so how exactly does one "discharge it an then liquid fill with correct amount?" Which control am I trying to rest with DAS? I take it the DAS reset is not the same as the CCS hidden menu code clear / reset technique? (toggling each auto button when in the REST + record menu)?

Thanks

 

The pressure in a non-running (static) system containing both liquid and vapor (the usual condition) depends only upon the system temperature. In a system containing refrigerant R-134a, a pressure of 90 psig indicates a system temp of 82 deg F.

That is all that you can conclude from the static pressure.

 

You're so right, Wally, but if the system is locked out it should have been low when running. Who knows, maybe somebody overcharged it, then other faults would register.

 

Makes perfect sense, thanks for that. I think I understand about the lack of compressor clutch being significant... You mean that a typical A/C shop can't just arbitrarily engage (energize) the clutch to get things moving again to charge the system? So is the compressor just always engaged and "throttled" by a pwm controlled (duty cycled) bypass valve?

 

Hi All and thanks for the responses. So the bottom line here is that low refrigerant, can if undiagnosed, cause the system to enter a "protection" mode where the compressor is effectively disabled which requires STAR DAS to reset?

 

yep