Your HVAC control box is full of switches. They do get dirty.

I also do electronics repairs.

While I had the heater ripped apart on my 190E, I cleaned up and did a fair amount of circuit board soldering on my control unit. I found a cold solder joint at the fuse itself on my unit, for starters.

Mine is working fine now.

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.