I just bought a 2003 GMC ENVOY SLT w/ the 4.2L 6 cylinder.  I am having trouble w/ the A/C it will blow nice and cold on the drivers side but the passenger side and rear are blowing HOT air. I have been on quite a few forums and there are tons of people having this problem but nobody seems to have the answer. So if someone could help me out I would greatly appreciate it.

THANKS in advance. I have already checked all the fuses, none are blown and none of the modules look or smell burnt.

Answer: Yes, the problem with the front is a common thing. The cause is a part called the passenger side temperature door actuator motor. As it's name implies, this electric motor controls the temperature of the air coming out of the passenger side vents. There is also one for the drivers side and the rear vents.

If you search our site for- door actuator, you will find several articles.

It would be strange for the passenger front and the rear actuator to go bad at the same time. It is possible the rear had failed some time ago but no you just noticed it.