latley now that the weather is cold and i use defrost i cant switch out of it with out turning off the truck shutting off the switch setting the dial to floor only then i can restart the truck and itll be fine. also when it is on defrost both left hand lights are on for rec and i think its fresh. i cannot turn ither of those off when it does this. anyone know where my problem is at?

 

Just did it by its self on the way to work dial was set to floor and it changed to defrost by itself?! Wtf

 

Sounds like stripped out air door motors. Pull the mix door motor off and see if it is loose/broken when you command a position with the dial. I think you can get to it by the bottom left of the glove box, a Haynes or ALLDATA would be able to show you.

 

The mode door actuator is on the side of the a/c box to the right of the gas pedal. ITs a pain in the *** to get to. Could be as simple as the actuator failing or when those trucks were new we had lots of problems with the early control panels. I'd start with the control panel first because the actuator cannot move unless a signal is sent to it initiating the move

 

Some how my headlights are making it do this! I've noticed if my ballest doesn't fire and only one headlight comes on it will make the unit do this. I was driving and to make sure this was what was doing it I had my brights on then flick it off and only one light came back on low. Flick it to high then back again and it kicked the hvac to normal again. It's done this several times now in the last week. I am going to splice in a new connector for the headlight and hopefully get a new ballest sent to me