My MM has a sliding lever to control the temperature. This is not to be confused with the blower control.

When I slide the lever from hot over to cold it gives resistance when pulled toward the cold side and then it pops behind the dash and the lever then moves back to the middle. It will blow hot air all the time.

Can that lever be accessed from under the dash so I do not need to tear the entire dash apart? I am assuming something must be caught in the flapper or it is rusted on one side.

The windshield was leaking for a year when the truck was sitting and we did not realize it. Now the heater control lever will not stay over on the cool side.

options on the problem and easiest fix?