Heat Problem

[dieselbeagel]

My car, 83 300D Turbo, 319K miles seems to forget the heat setting after about driving for about 30 mins. I get heat blowing thru the 2 side vents. After about 30 mins, it then starts blowing luke warm air thru all 4 front vents.

I have to turn the dail on the CCU up (more heat) for the heat to come on again. Heat once again comes from the 2 side vents.

Is this normal for the heat to go luke warm or is some unit in the car that needs attention ?

[sixto]

The cabin temp sensor might be senile or the foam hose leading from the sensor to the blower chamber has disintegrated.

If you can correlate loss of heat with rise in engine speed, it could be a leaky monovalve cartridge.

Are we on for Sunday at 9am?

Sixto
95 S420
87 300SDL

[tangofox007]

Originally Posted by sixto

If you can correlate loss of heat with rise in engine speed, it could be a leaky monovalve cartridge.

True. However, the fact that the center vents are coming on concurrent with the heat loss would tend to rule out a monovalve malfunction. A monovalve leak will cause a loss of heated air, but it will not cause the vent configuration to change. If the center vent flap opens, it suggests that the CCU "thinks" that it is in the cooling mode.