the air vent on the lower portion of the dash board near the door handles blowes very hot air in the summer and cold air in the winter, even if the blower is turned off. The blower motor is not running it is like some door is not closing all the way allowing for air off the engine to come blowing into the vent. It sounds like a vaccum problem to me, if anyone else has an idea about it or has had a similar problem please let me know. It is on a 1982 300 SD (126 Sedan)