I have a 2010 ford fusion. After letting the car heat up, I went to the store and the heat was working fine. I get back home while parking I noticed the car was blowing cold air. I cut it off and then back on and the same thing; it didn't get hot again. It was fine last night and a few minutes ago. What could of happen that quick? Since I tried cutting it off and letting it get cold again, then warming it up, I still get the same results. The heat is blowing cold. Any ideas on what I could do?
There are two possibilities here as I see it. First, it could be that the thermostat is bad and stuck in the closed position, not allowing hot coolant to flow into heater core. You could easily check to see if this happening by first finding the heater hoses which route from the engine through the firewall of the engine compartment. With the engine warmed up, check both hoses to see how warm they are. If they are not very warm, this is probably your problem. If both are very warm, the blend door which routes the air through the heater core inside of you cabin is probably stuck in the "cold" position. You'd have to tear the underside of the dash apart to get to this.