I have a '01 with about 145,000 miles. 2 months ago my mechanic ran some cleaner though the vacunm line to clean up the intake manifold . after he did this the code cleared, but I had a funny noise under the dash for a couple of times after this was done. the heater seems to work good when I first run the truck to an from work, about 25 min drive. the other day I had to take a longer drive and the heater only put out hot air when I started up the truck when it was hot. Turing the temp **** made not difference. this weekend I had to take another long drive. When I first used the truck the temp could be controlled by the temp ****. When I restarted the truck the heater only put out very hot air. I even put the thing on A/C and it put out hot air. Then when I was coming home after about 1 1/2 hours of driving , it kind of stated to sork OK. It would change from hot to cold about every 45 sec or so. Where do I start to check? Could the cleaner have gotten to something an melted something?

 

Unrelated.

You have a temperature blend door problem.

 

How can I tell if it is the door or the motor?

 

Take the motor out and test it.

 

What i mean is the actuator/motor. I though that I read not to run the actuator out of the dash/unit. Sorry about this, but I am not good with electric things.

 

Got time today to take the thing apart to find out what was wrong. Found out that all that I needed was just the motor for the blend door. Getting out the screw in the back of the air duct was a pain to get out, was not able to get the screw back in the hole.