82 300SD Heating problem
 

The car will not heat properly. It would blow cold air at a high level when the outside temperature was cold. It blew hot air at a high level when the outside temperature was warm (50 degress or more). Once in a while it would operate properly. Now it just blows cold air regardless of the outside temperature.

WHAT SHOULD I BE LOOKING FOR??? And where it the thing I'm supposed to look for located?

Richclay

heating problem diagnosis
 

Hard to tell based on limited information, but....

1. check to see if engine temperature gets up to normal (85 - 90 C)...if not thermostat may be bad. The erattic behavior is also consistant with a thermostat going bad.

2. In your 82, I think you have the automatic climat control, but I dont know if the same as my 85 300D....but probably similar...could be inoperable "mono-valve"...this controls flow of hot coolant to heater coil, controlled by signals from push button climate control unit. Rebuild kit costs about $35 and takes about a half hour to complete.

3. Malfunctioning pushbutton control unit....cant be repaired by DYer if this is the case....rebuilds cost about $100+

good luck,

Mark

The mono valve is most likely your problem. They are easy to rebuild. On the 123, it is mounted on the firewall. It is square on top with a cylindrical center piece.