Heater Level Stuck on Hot
 

My wife's 2002 Explorer heater temp seems to be stuck on high. When the engine is running, turning the heater temperature adjust knob from high to low doesn't seem to change the temp or if it is, it is very minimal. It blows maximum hot and turning it all the way cold changes it very little. Seems like a little temp change moving the temp control knob from max heat back to 1 o'clock position. Can also hear movement...not clicking.

Wonder if I have a broken actuator gear or broken blend door. Seems the door wouldn't move at all if the axle was broken. With the slight temp change moving the knob, I'm thinking maybe the actualtor gear has broken a couple teeth amd jamming.

Thanks.