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kurtfire5

M Klasse Defrost Problems Low Heat Output

My 2002 Mercedes M Klasse with a gasoline engine has a weak defrost. Vents are blowing but the heating output is too low. I pulled the codes and found an error related to the air distribution flap. I suspect a bad connection but am wondering if anyone has seen this before? Mileage is at 269461 km.

Summary of the thread

The 2002 Mercedes M Klasse is experiencing weak defrost and low heat output, with an error code indicating an issue with the air distribution flap. The problem is suspected to be a bad connection. After investigation, it was confirmed that a corroded connector to the air distribution flap motor was the cause. Cleaning the connector resolved the issue.

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4 comment(s)

vincentschroeder1

I had a similar issue with my old Ford Focus, though it wasn't a Mercedes. The windshield fogging was terrible. Turned out the blend door actuator was faulty, causing issues with the ventilation system. Have you checked the heater core itself? Maybe it's partially blocked?

kurtfire5 (community.author)

Heater core check is next on my list. Where exactly was the blend door actuator on your Focus? I'm trying to get a sense of accessibility and if it's a similar design.

vincentschroeder1

On my Focus, the actuator was buried behind the dash, near the HVAC unit. A real pain to get to. Given the stored error points to air distribution, and you are experiencing low heating output, the flap might not be opening properly. I'd strongly suggest taking it to a workshop, the error memory points to a faulty component.

kurtfire5 (community.author)

Thanks for the insights. It ended up being a corroded connector to the air distribution flap motor, like I suspected. I cleaned it up and all is good. Total cost was 95€.

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MERCEDES

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MKLASSE