PeterOlajos

Good day everyone!
I have a 2002 SL500 and I'm desperate for help. The car is in almost perfect condition. I have bought it with a faulty climate control and have thought that it will be easy to repair. The problem is, that from time to time it won't cool the air. It decides it doesn't want to work anymore and then it blows air in from the outside, after a few hours or days it just turns back on. The heating is also faulty, either it is really hot or once again just blows in air from the outside. A Mercedes-specific mechanic told me that my climate-compressor is at fault, however during testing it was shown, that it works adequately, it just doesn't receive power from time to time. He has concluded that the fault is either in the climate contol unit OR the climate control panel OR somewhere in the wiring between them. He has no idea what the next step should be? Could you please give me ideas and opinions? I'm open to other possibilities too, I'm not exactly convinced that this is really the origin of this problem. Thank you in advance!

Rudeney

The ACC system has DTCs that can be scanned and will likely give some clues as the the culprit. A generic OBDII scanner won't do it - those only scan the ECU and not the other MBZ systems. Of course SDS (the Dealer's Star Diagnosis System) will do it, but there are other tools, too. iCarsoft i980 is one that is not too expensive - it will read and reset all codes form all systems, but it won't do any coding or actuations like SDS. If your mechanic does not have tools that can scan beyond generic OBDII codes, then you might want to find another shop. In fact, on the R230, it's pretty much impossible to maintain it without SDS.

Regarding this problem, since it affects both heat and cooling, and it does work sometimes, I doubt it's the AC compressor. It certainly could be a bad ACC module, or, it could even be a bad humidity sensor (it's located in the overhead control panel). I am not sure with the R230, but in the W209, it ignores that sensor with the top open, so that is one quick way to test it without a scanner (i.e. if the AC works with the top open).

PeterOlajos

Thank you for your reply! The diagnostics were indeed done with SDS. That was the one to show the climate compressor and the upper control panel(the one on the top of the dash which has 2 buttons and 3 potmeters) as faulty. But during testing we came to the conclusion that neither of them cause this problem. (The fault-signal of the panel is not constant and its detached from the fault of the climate control.) Also, my problem exists with the top down too, but it tends to be a little bit better when the top is up (that can also be accidental).

Rudeney

Did you happen to get the exact codes? There is no code for "bad compressor" or "bad overhead control panel", but there are codes that will lead one to diagnosing those as defective.

Since you say you had an OCP error, I'm betting it's the humidity sensor. Officially, this requires replacing the entire OCP, but there may be a better solution:

http://www.benzworld.org/forums/w220...lp-c-diag.html

PeterOlajos

Unfortunately I didn't. We are talking about different panels here. The one that was shown in the diagnostics was not the overhead one, but the one on the top of the dashboard. But as I have said, it doesn't always give the fault-signal and my problem isn't affected by it. I will try to perform the diagnostics in the link you sent me and post the results.

PeterOlajos

This kind of diagnostic does not exist in my SL.

Rudeney

In SDS, choose Control Units -> Body -> OCP

Here are its possible DTCs:

http://benzbits.com/R230/R230-DTC-OCP.pdf