Hi All,

2010 E63 AMG - 99k well maintained miles

A few weeks I started my car and the AC was blowing hot air. After 10 minutes it blew cold but then after a minute or so it went back to hot. After I parked the car overnight it started up and blew cold for multiple days. Then out of nowhere started blowing hot again. So I took it to my shop and they couldn't replicate the issue. The AC was blowing cold. They checked the refrigerant was full and the high and low pressure was where it should be and left it on the machine and found no leaks. No trouble codes were showing. They were convinced it was the "heater control valve". More specifically the diaphragm was not opening and closing properly. They replaced it and for about 10 days straight the AC has been working great, until today. So it seems like the heater control valve was not the issue.

I got in my car after work when it was 92 degrees outside. Blew cold for about 5 minutes then hot the rest of the way home. I scanned the car again. No trouble codes. When the AC is acting up and not blowing cold air, the idle is a little rough. The rpms never drop below normal idle but they will periodically jump a little. The car never feels or sounds like it’s gonna die. When the AC is working properly, the car idles perfectly. Any suggestions on where to start? I plan on getting back to the shop next week but I’ve got a free weekend and would like to start troubleshooting on my own.

Thanks

 

Compressor
https://mbworld.org/forums/c63-amg-w...g-hot-air.html

ac clutch for compressor
https://mbworld.org/forums/e-class-w...est-drive.html

this could explain the laboring idle

 

Do you have an MB-aware scanner? XEntry or Launch X431 CreaderElite for Benz?

You can monitor the AC module when working correctly, and when not.
1 - Check if the compressor is being activated, also confirm you can manually activate it using the scanner.
2 - Check for refrigerant pressure on both cases
3 - Check for the electronic control valve duty cycle as well. You can also increase the duty cycle and see if the cooling improves.

Of course, an external set of AC pressure gauges would tremendously help monitor the low-pressure side when diagnosing the system.