I have an '02 GMC Safari van. One morning my window started to fog up so I turned on the defrost. It got worse!. The air blowing out of the vent was cold even though I had the heat turned all the way up. I tried the floor, vent, everything they all blew out cold air even with the heat all the way up. Checked for leaks around heater core, none. Checked coolant in radiator, full. Any suggestions?
There’s a blend door in the ventilation system that directs either outside air or heated air out the vents. If this door fails to go to the position for heated air, you’ll get none.
The vent system in your vehicle is vacuumed controlled. So look for a binding blend door, or an inoperative vacuum control motor for the blend door.
Tester
I would suggest that you consider the possibility of a leaking heater core.
Even though you apparently have not yet detected the tell-tale odor (sweet, almost like maple syrup), this has other hallmarks of a leaking heater core.
Keep checking the coolant on a daily basis. If you do detect a drop in coolant level, that would help to confirm a leaking heater core.
Thank you to the top two replys, I’ll check out both.
Do You Know That The Engine Is Getting Up To Optimum Operating Temperature ? Do You Have A Coolant Temperature Gauge ? Maybe The Thermostat Is Stuck Open.
There could be air trapped in the cooling system.
CSA