I have an 07 freestyle that has no heat except when its turned to the highest setting as soon as I turn it down it get cool instantly. I did change the thermostat and the old one did have a weak spring and the engine temp would drop while idling at lease now the engine will hold temp. With the temperature set to the highest settingthe air is hot the only way I can control the temp is to reduce the speed of the fan. I am now thinking it has something to do with the mixing chamber or the temperature sensor. Any ideas or suggestion would be greatly appreciated.
The F150 and Explorer work like this... not sure of the Freestyle.. Hot air from the heater core and cool air from outside are mixed together in a mixing box. There is a motor controlled damper door that you adjust from open to close with the heater **** on the dash. This is called the "blend door" The larger trucks have had troubles with the control arm on the door breaking, or the electric motor drive failing. NOrmally the location is above the transmission hump, below the radio, left of the glove box. You can normally take off the plastic dash section below the radio, above the hump to get access. Some vehicles you have to remove the glove box... I hope this helps. I assume the Freestyle is similar to the Explorer..