the air conditioning stops working randomly

I have the same issue with my AC ( GL450 2009), i took it to Mercedes dealership and they too are guessing what might be the problem. They wanted to change the Climate Control unit for $1700 and that is not guaranteed that will work. Did you find out what was the cause?

Hey Guys,

Yes this is a climate control issue that will end up being the controller, try to get one from a wrecking yard it will be less money. Mercedes parts do cost a bunch and they just want you to buy a new car most of the time.

Please let us know happens so it will help others.

Best, Ken

I have the same problem with my 2009 GL 550. Air conditioning is ice cold at times and then just starts blowing warm air for no apparent reason. It does this regardless of whether I have setting on automatic or not. Eventually it may or may not come back to cold air. I took it to a Mercedes dealer and they installed a new compressor and compressor wiring harness. Didn't solve the problem. Took it back and they still couldn't pinpoint the problem. Eventually took it to another Mercedes certified mechanic and they replaced the receiver drier and expansion valve. After nearly $6000 in repairs... it STILL doesn't work correctly. I'm obviously a little hesitant about spending any more money on this, so how certain are you that the climate controller could be the issue? Thanks

Mercedes Bends have a history of the controller (Panel) being an issue for intermittent problems. The only way to be 100% sure is to do some testing at the controller to check the voltage input and output while the system is not working.

Here is a guide and a wiring diagram (diagram) so you can do some testing.

https://www.2carpros.com/articles/how-to-check-wiring

and

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please let us know what happens.

Cheers, Ken