Chevrolet C/K truck mode and blend door actuator replacement
Here's a video covering a common repair issue on GM C/K series trucks.
If you are having problems with no heat, no cooling or air coming out from the wrong place and you've confirmed that the control panel isn't burnt up, then chances are you have a failed actuator.
Air door actuators are cheap and fairly easy to replace on these vehicles. However, ensure that the control panel IS functioning and sending commands to the suspect actuator before condemning it.
There are three actuators which do three different things, so make sure you have identified which one is defective before buying a replacement.
1. Mode door: Mounted on end of case near driver's right foot. Controls where airflow comes out at.
2. Blend door: Mounted on rear(tailgate side) of case roughly behind the ashtray. Controls how hot or cold air is.
3. Recirculate door: Mounted on top of case, very hard to access. Controls whether air is fresh or recirculated. Most people don't bother replacing it.
WARNING: DO NOT "TEST" ACTUATORS WITH THEM DETACHED FROM THE HVAC BOX!!! THEY WILL OVERTRAVEL AND BE OUT OF INDEX AS YOU'LL SEE IN THE VIDEO. YOU CANNOT REPAIR THIS EASILY, SO ALWAYS HAVE THE ACTUATOR MOUNTED TO THE BOX BEFORE ANY KIND OF TESTING TAKES PLACE.
ALSO, INSPECT THE FLAPS THEMSELVES TO ENSURE THAT THEY ARE NOT HANGING UP. AS WE ALL KNOW ANYTHING IS POSSIBLE WITH GM.