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First post here but not new to the rodeo. Can anyone tell me from experience which of these stepper motors controls the hot side blend air? I have only a faint amount of heat coming out (engine temp 82*-84* C) of any vents. Setting the climate controls on both driver and passenger side to 66*F causes normal volumes of cold air to get through fine, but increasing either side towards 80*F causes the flow of air to be very restricted, and not hot. I have gone through the "reset" procedure with the climate control button, and as the cycle completes, once again the "hot" air gets starved off from all vents/footwells. Before I start to peel the dashboard apart, I would prefer to know which one of these actuators (stepper motors) is the "king of hot".
Strange, there will be 2 blend flaps left and right side. Do you hear any clicking sounds from these motors? The best way to diagnose it is with a scan tool where you can see each motor position and also actuate them individually.
From everything that I can piece together from various forums, these two actuators control dampers for heated and fresh air flow independently. There is a diagram posted in this W203 section that shows the air flow travel pattern, and indicates these actuators to be the major players, just not specifically by task. There is no snapping nor any clicking noise, so dead actuator, or totally broken linkage. My scanner does not decode for this car for whatever reason...good on my Jetta (2008) and XC70 (2007).
It may not be a broken linkage, but a broken gear tooth. Happened to me a few months ago and suddenly my windshield defrost stopped working on day. In this scenario, there will be no noises as the actuator still spins away. Not sure if your car has 6 or 10 actuators (there's no W203 C280 over here) but hopefully this will point you in the right direction.
In any case you have to rip the dash apart to access the motors. The 2 motors in question here are both on each side of the box, and therefore will require removal of both the glove box and panel under the cluster (ie where the driver's and passengers knees are).
Last edited by slammer111; Jan 10, 2018 at 12:44 AM.
Thanks for the reply; I have been recently told that the M2/6 actuator ( behind drivers side panel) is the one in control of the hot air flow, so that is the first target. My W203 has ten (10) of these same actuators, and I am not looking forward to having more fail, definitely a weak spot in M-B design IMHO...
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