This 2003 GMC Envoy came in with the complaint that the a/c will only blow out the defrost and floor. Not through the dash vents. I checked codes and found a code B0263 for a fault with the mode actuator. I first ran into this problem after changing a battery in one of these vehicles last year. Whenever the battery is disconnected the HVAC unit will perform a recalibration of all doors. This causes the door motors to be moved full cycle and the mode door will stick some times. I now hook a jump box to the system before changing the battery in Trailblazers or Envoys to prevent a recalibration from occurring. This way I will not be blamed for a stuck actuator motor.
Anyways to change the actuator motor, first drop the hush panel under the driver’s side of the dash. There are some parts that have to be disconnected from the panel including the turn signal flasher assembly shown in the next picture.
Next, I removed the lower dash knee panel to have a little more room to work.
I had to pull a push pin retainer out at the left side of the duct work in order to remove the driver’s floor vent.
Now, I could finally see the actuator on the side of the heater a/c box.
I removed the actuator and installed the new one. Performed a recalibration with my Tech 2 and put all the panels back in place. A recalibration can be done by disconnecting the battery for at least one minute, reconnect the battery, start the engine and leave the a/c controls alone. I would recommend letting the engine run for at least two minutes, turn the ignition off for at least ten seconds but no more than thirty seconds and then restart the engine so that confirmation of the repair can be done.
I do not recommend connecting the wiring to the actuator until it is installed. They come prepositioned for easier installation.
The notch at the lower edge of the gear is an alignment point. There is a corresponding tab on the door linkage that needs to be lined up with this notch.
To purchase the mode valve actuator, please click here. To see updated information about actuator positions and alignment, please click here.
It will have the white gear attached. To see the correct actuator, you have to look up and to the right, while laying under the driver’s side of the dash. It is near the rear corner, driver’s side, of the radio and a/c control head.
Thanks for this site! I have an 03 Trailblazer extended with the same problem. I bought the part linked to #52411434 and am attempting the install. The actuator I removed is part #52402611, seems to be in the same location you referenced. The actuator in my car does not have the white notched cam at the top just a round stud where possibly the cam is inserted. There is another actuator next to this one with part #52402610, it doesn’t seem to have the white notched cam at the top either. Am I working with the wrong parts or is the cam stuck inside the housing, I’ve looked it doesn’t seem to be the case. Appreciate the help!
It sounds exactly like the same problem.
Hey, I just installed a new cd player in my car (2004 chevy trailblazer), which required me to disconnect the battery. When I connected the battery back, all other vents has air coming out except the dash vents. Could this be the same problem mentioned in these posts?
I have a 96 gmc sierra with the same issue as the 2003 envoy. Can I do a recal by disconnecting batteries? All actuators seem to work