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.
really good site, I have a 2005 silverado with the same problems, air only comes out of the defrost and floor vents,fan works on all speeds, it is has auto controls,What is the part number for the actuator and where is it located. thanks KB
I have a 2006 Envoy. I changed the battery out and sure enough, I am not getting air through the front vents. I took your pointers and changed out the actuator. It went pretty good. The only thing that was confusing to me was when I could see the actuator, there were two of them right beside of each other. I had to stop and make sure which one I was to change out. Thanks for the tips.
The full sized trucks have more of a problem with temperature actuators being set out of calibration when the controls are adjusted before the process is completed. If you are having mode problems the mode actuator is likely to be at fault. It is a different part number than the one in the post. If you need this part email me and I will be happy to supply a link. The comment area in this site does not support links.
Hey Sparky! Same problem as described throughout the post, with my 2002 Silverado 1500 pickup…you said
“The full sized GM trucks have a differnet issue with the a/c when the battery is disconnected. The system will still go into recalibration mode but the actuators generally get stcuck due to operator error, especially during the summer. Do Not Touch the a/c controls for 1-4 minutes, depending on year model, after the battery is disconnected and the engine is restarted. After the engine has run for 1-4 minutes switch the ignition off for 10 seconds and restart. The system should work okay.”
Is this actually a different problem than what’s described? And should the controls be set to any certain position when recalibrating? Finally, if this procedure doesn’t fix it, time to replace the actuator, right? Is there a different p/n for ’99-’02 full size pickups?
Thanks for the help! Awesome site!
Hi 96 GMC Sierra,
Near as I remember they work a little differently and self adjust when a new on is installed and the ignition is switched on. Do you only have air coming out of the defrost? Do you have any meters to test with?