Hello All,
I have ML320 2002, my A/C started to blow hot air couple of weeks ago, I took it to A/C repair shop, and he checked the pressure, and decided to clean the system, which he did. A/C worked again with nice and cool air. Then one week later, hot air again, I parked the car for couple of hours, and then I tried it, then A/C worked gain. It continued working for few days and then hot air again. I waited for few days before I took back to the same shop. Mechnic checked gas presure and computer codes and nothing registered. The problem according to him, that Compressor is not engaging. When hot wired the compressor it worked and blew cold air.
One strange thing that the Aux fans are always on all the time, with A/C switch on or off. He checked A/C ACC temperature switch, said it's ok.
I belive there has to be a relation between Aux fans being on all the time and compressor not engaging? any help is greatly appreciated.

Thanks for all the help

1) Verify that the compressor is actually turning when it is blowing hot air.
2) If it is not turning the problem is likely wiring related. Check continuity and clean all connections.
3) If the compressor is turning then it is likely the mixture blend door control. Search on Youtube. There is a video on how to replace this item.

You need to go to a MB shop that can check the controls that turn on the system.

A scanner that can read live data on the A/C/C system is required.

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Thank you for the advice, I think it's dealer $$$$ time.