I didn`t drive my car for a week. Then drove it around for about 20 miles whyen suddenly the heat stopped comming out of the fans. No problem I thougt because I have a small leaking problem and thought that the coolant is just a little low. Ok went home, filled it but nothing!? The car does not over heat the cooling fan comes on normally but no heat. Everithing is normal exept for the interiour warming.
I tried to air the system but it did not help.
Somebody help me please!

 

Check the doors in the ducts if for some reason they closed up especially if they are electronic control and not cable controlled. also you might have a blockage in the line going to or out of the heater core, the lines going to the firewall, especially if you have used a lot of stop leak lately I've seen that clog stuff up or they may have a kink or collapsed totally.

 

Also, your heater control valve (if your car has one) may have failed...

 

It is probably not the doors or ducting. The doors in the ducts just direct the flow of air either to the defrost vents, the dash vents, or the floor heater vents. You should have hot air coming out of one of those three places when you turn on the heater, and fan. I sounds to me like a heater valve stuck closed.

 

Had this happen to me, It's your thermostat stuck in full open. No heat can build up in your car to be sent to the interior. Pull the Thermostat housing and you'll probably find the copper plug mashed down and wide open. Mine failed in the middle of winter, ever try to air the system in -30 C weather?


Not fun

 

Thanks for all of your help, but as suddenly as the problem appeared it disappeared!
It is still a mistery to me but it s fine now and I am happy !