I have a recently acquired (Oct./99) 1990 300D (North American version), and when the temperature gets cool here (-20C or about -4F) I find that my MB does not heat particularly well inside.
At highway speeds, after even 10-20 minutes of operation, I find its necessary to leave on my winter coat, have the temperature wheel set to MAX and the re-circulation engaged (in EC mode, AUTO fan speed). Its just about luke-warm inside (not as warm as I would like)
Is this normal? The engine temperature is at its normal operating temperature, no windows are open. Is this related to the mono-valves (perhaps torn)? I was considering putting a rectangular piece of cardboard in front of the radiator while the weather stays cold here to limit air flow through the radiator (I used to do this with my volkswagen all the time in winter... helped a lot).
Any help warmly accepted (brutal pun acknowledged)