I haven't run across this particular problem throughout the reading of the questions in the archives.

If my 300D has been sitting for 15 minutes to an hour, as soon as I start the car backup, heat enters the interior (the fan needs to be on of course). It seems as if the mono-valve leaks heat into the heater core even though I have not run the heater. My mono-valve performs normally while the car is running, but the amount of heat that enters the a/c system while the car is shut down seems to be abnormal.

Anyone? Bueller?

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)