Took a quick drive to the store just now and thought I'd try the heater again. I noticed very moist warm air coming out the driver side vent but as soon as I upped the blower speed the heat dissapeared. Does that stroke with the monovalve scenario?

This problem is new to me too - had the opposite dilemma on both my previous 124's. The car is a RHD - I've downloaded a pic of LHD engine and will compare layout this evening.

Thanks for all the input so far!

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1993 280E

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Past Mercs:
1988 200
1984 230E
1977 350 SE