Mercedes X Klasse AC Issues

That sounds eerily familiar. I also own an X Klasse with, I suspect, the same diesel engine. I had similar cooling system problems last summer. The AC unit issues manifested in much the same way: intermittent cooling, eventually no cooling at all, and a rather persistent warning light. Before condemning the control unit entirely, have you checked the basics? I am thinking about simple things like the auto refrigerant level and the compressor clutch relay? It would be a shame to replace an expensive component without ruling out simpler causes first. Were there any unusual noises coming from the compressor before it failed completely?

Thank you for your prompt response. Regarding your suggestions, I did indeed check the refrigerant level, which appeared to be within acceptable parameters. However, I must confess that I did not specifically examine the compressor clutch relay. Could you perhaps elaborate on the procedure for assessing its functionality? Furthermore, concerning unusual noises emanating from the compressor, I recall a faint, high-pitched whine preceding the complete cessation of cooling. Is this potentially significant in your estimation?

That whine is certainly noteworthy; it could very well indicate internal damage within the compressor itself. As for the relay, swapping it with an identical one from another circuit (horn, perhaps) is a quick test. If the AC then functions, you have found your culprit. However, given the whine and your prior checks, I suspect the compressor is indeed the issue. I ended up having to replace mine. I would advise taking it to a reputable workshop for a proper diagnosis. It is possible that debris from a failing compressor can contaminate the entire system, necessitating further flushing and component replacement, which drives up the cost significantly.

I sincerely appreciate your insightful counsel and shared experience. Based on your recommendation and the corroborating symptoms, I shall proceed with a comprehensive diagnostic assessment at a trusted workshop. Your cautionary note regarding potential system contamination is particularly valuable. I will ensure that the workshop meticulously inspects the entire automotive cooling system for any debris or consequential damage resulting from the compressor failure. Thank you once again for your invaluable assistance. It appears likely that I am facing a substantial air conditioning repair bill.