Grand Am GT 2003 Heat Problem

Hello All, I have a Grand Am GT 2003 with a problem...My heater only works when the dial is turned all the way to the right (hottest setting). When the dial is pushed up even a bit, the air goes from hot to cold instantly. There's no in between like there used to be when I bought it. I have no idea what it could be, but my girlfriend thinks it's the thermostat.

It's definately not the thermostat.

Check the temperature switch to make sure it's not shorted causing everything coolor that hot to be the same. Also and the blend-door actuator.

Welcome to AF.

So are you saying your heat isnt hot and your blowers not working only on high ? If the blower isnt blowing on all settings check the fuses and see this thread if they are OK.
http://www.automotiveforums.com/vbulletin/showthread.php?goto=newpost&t=665246

On the temprature, could be the thermostat, could also be the blend door on the hvac unit under the dash, no fun thier a real pita to work on.

If the thermostat was the issue then the temp gauge would read a lower operating temp the usual.
Could also be you have a 185 deg thermostat, and if its realy cold out the heat settings can be cooler then norm.

A complete cooling system flush may even be needed, gonna take some trouble shottin on your part.

hope that helps.