i have a 1984 mb 300d with climate control.
on a long trip i took today the heat cuy out, all i have now is cold air blowing out, even in the defrost mode.
does anybody know why this happened ? if so how do i fix it ?
thanks

Did you watch the temp guage? If it took a really long time for the engine to heat up your thermostat may have failed. If this is the case you would have trouble getting hot air. If not there are a few other things it could be. Mostly likely the monovalve (I'm not sure, but I think your model has one) or at least the monovalve insert. I had the monovalve insert replace in my old 420SEL and got my heat back 100% right away.

__________________
Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired

temp gauge i have no problem with

I'll bet it's the mono valve. It's very east to replace. You can get one here at Fast lane for about $35.00. The mono valve is located at the center of the firewall. It has a square top that has four screws, one at each corner and a round (about the size of your pinky) metal tube sticking out the top. Simply remove the screws, pull off the top plate. Then withdraw the tube thing that was sticking out the hole in the top (that's the mono valve) Pay attention to the order the washers with it come out, then replace the new valve. It should only take 10-15 minutes.

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Mr. BILL

91 300E 120K
90 300SE 275K (sold)
92 BMW 525iM 120K
90 BMW 525iA 175K
85 300D 175K (sold)
84 300SD 245K (sold)