Heater Inop
 

The heater in my 1993 M-B 300D 2.5 turbo has discontinued keeping me warm in cold weather. What should I look for inorder to get warm again?
Thanks for the help, Lgriffi

I will assume the fans are working but no hot water...? Do a search for mono-valve.

I just fixed one of these - symptoms - no, or very little heat. Ended up being what I would refer to as a monovalve, but I believe in your car it is called the water valve, in any respect it is a royal PITA to get to and the part is quite pricey. The reason was that the monovalve and recicuating pump are one unit. Up by battery. Rule out other obvious stuff first like fuse, thermostat ect

You should be able to bypass the recirc pump/water valve with straight hose to test it. Little heat will come out at idle or low engine speeds because the water pump doesn't put out enough pressure to get back to the heater core well. At higher engine speeds it will pump heat out.