Why is heat comming up through the vents in my chevy s-10? with the blower off and the thermo on cold. ?

Question

The A.C works but when its off i get a steady stream of hot humid air through the vents. the hot cold switch works fine The windows dont fog up. Any Ideas?

Answer 1

You may have it set to refresh the cabin air. This lets air move through the heater ducts when the truck is moving. This coupled with worn gaskets that controls the air through the heater core could/would result in this problem.  

Answer 2

I THINK IT WOULD BE SAFE TO SAY THE AIR ISN'T WORKING,IS THE BLOWER ON OFF OR ON?

Answer 3

Set the vent to recirc if you can.  The blower always works at low speed so it is not unusual.  The vent door may be stuck open because of a broken or cut vacuum line or just debris.