Hi All,


I purchased by 1983 300 Dt in November 2009 so this is my first summer with the Frau. The AC worked well as it started getting warmer. We have had a nice hot summer in Atlanta and I'm getting some interesting behavior from the AC.

On the hottest days when you start out, the air blows cold and the car is comfortable. As long as you are driving it is fine. When you stop to go into a store or something, very often when you start back you get an intense blast of heat out of the vents for at least 3-5 minutes. Sometimes the cool kicks back in and other times it doesn't. It is not just lukewarm air but feels like it is actually heated.

When I get back home and the car sits for a while, I can start back up and the cool air is there. Now this does appear to happen only on the hottest days (90s). The engine is not in a overheating situation. The temp gauge shows around 80 - 100.

The records show the car had a new compressor 3 years ago. I did recharge it with R134 and it took about half a canister. I have tried turning off the air - pushing the Economy button, adjusting the climate control knob and leaving the air off when I start but nothing seems to change the pattern.

Appreciate any thoughts or suggestions of where I might begin the diagnosis process.

Thanks!
Gib

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1983 300Dt 142K Miles

So where the hell was Biggles when you needed him last Saturday and where are all the sportsmen who always pulled you through?

The problem is the check valve in the monovalve assembly. The monovalve is held closed electrically. When you shut the vehicle down, coolant floods the heater core, giving you the blast of hot air at subsequent start-up. (The check valve is supposed to prevent that condition.) The easiest solution would be to plug a heater hose until November.

Cleaning the check valve (bottom end of monovalve assy) might provide some relief. (Mine is clean and I still have that problem on occasion.)

Great! Thanks so much!
Gib

__________________
1983 300Dt 142K Miles

So where the hell was Biggles when you needed him last Saturday and where are all the sportsmen who always pulled you through?