my mechanic have fixed this once he said it's something to do with flaps. but after 2 years it gave out again. my car has 185k miles paint is fading and i'm not sure if it's worth to fix the air conditioner for this car. The heat comes and goes it that not do it every time.
airconditioner- heat comes out of the vent by windshield even the unit is on Off on 1994 Mercedes-Benz C220
poss jst a vac leak that controls door flaps. have you tech ck vac hoses it might be a simple fix