A good friend of mine has a 1994 C220 and the heater does not seem to be working properly. It is quite cold here (-12C), and none of the climate control buttons do anything. Yesterday after he left it running for over an hour, he came out and the fan was running and it was tosty inside. The engine temperature seems to be reading fine on the gauge. Any ideas what might be the problem?

Thanks,
Steve

On this & "almost" all MB's there is a heater valve that closes when a 12V power signal is sent to it. Try disconnecting the electrical connection & you should have FULL heat. If not then the heater valve isn't allowing water to flow OR the heater core is partially plugged.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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The heater and fan will come on now once in a while on its own. Sometimes after 40 minutes of driving other times right away. The display and all the buttons seem to works for the HVAC. It is really cold here (and hard to see without defrost).

Sounds like you mean the blower doesn't work at times?
If that is the case then you need to find out if the blower motor OR blower regulator(electronic) has failed.
Both are under the rt underdash panel, next to the micro(dust) filter.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Hi M.B. Doc,

How do you test whether the blower motor and the blower regulator are working properly?

Let me know. Thank you.