yourbenztech

I am working on a 2000 ML430 with AC problem, I may have misdiagnose the problem or can't see the whole picture and now I'm stuck, the symptoms where, the AC blowing hot air in in every mode, I checked the compressor no problem, low flow was cold, refrigerant level was right everything looked and checked good which brought me to the assumption that it might be the flap motor, I removed the dash and checked the motor and it looked as if it was locked on hot mode, trying to turn between cold and hot did not move the lever, I removed the flap motor(actuator) and push the lever back to cold "mode" and everything was working fine wile cold air was blowing through the vents, I ordered a new flap motor and installed but the problem consist, the motor will swing immediately upon contact with the wire back to "hot" mode and the hot/cold switch does not activate it, however, the flap on the passenger side does turn when I change the temperature which make me believe that the switch is fine....?? the new switch is original Mercedes and new, what are your thoughts and where do you think I overlooked??
I believe I wrote all the information, please help me if possible,

Maj. Dundee

The problem lies with the AC/Heater Control Module located at the base of the heater box. Do an on-line search with the complete Denso number.

R&I instructions call for removal of the center console, but the work around is to remove the center section cover plate and then the cover under the driver's side instrument panel, and then the AC/Heater Controls.

Look through the opening and you will see a foam covered box held by one Phillip's screw. With a long screwdriver remove the screw and hold it with your left hand through the opening on the left side of the console made available by removing the cover under the IP.

yourbenztech

Ok, great, I have the unit in my hand, I will have it ordered installed and update if it solved the problem.

Maj. Dundee

If you want to be sure then conduct the below test with a DVOM.

yourbenztech

When I unplug the AC control unit the compressor stop working, when I plug it back in the compressor resume..is that an indication that the unit might be good or just the compressor control is functioning?

Maj. Dundee

Are you referring to the control module, N19 or the control with the dials?

yourbenztech

Ok....update..(i wana scream) after replacing AC module, no change, motor flap will not respond, I proceed to changing control panel and still no results, flap motor still stuck on hot mode....I started to think what might tell the controller not to flip to cold when I realized that the temp sensor might be at fault..Ladies and gentlemen, the temp sensor is in between the aux and low range switch..If it is not working the flap will be stuck on hot mode..... and that brings a three days long diagnosis to an end!!! thanks the kind lord! and Mr. Dundee..