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.
Hi, I have the same problem as the ones above. I have a 2004 Chevy Trailblazer. After the battery died I had it replaced. Now there is a grinding type noise under my steering column for just a few seconds. The air will only come out the bottom not the top vents. I haven’t checked the defrost or rear air in the truck. Also, when the air compressor kicks on my truck tried to die but doesn’t. Did it just lose its memory????
There is supposed to be a fair amount of extra work involved in changing the mode actuator if your vehicle has adjustable pedals. I have not done one myself so I do not actually know. I have been told by others that the gas pedal assembly has to be removed in order to access the actuator. As far as the temperature actuator on the passenger side goes, I would try a recalibration if the battery has recently been disconnected. If the problem persists, change the actuator. It is located to the left of the glove box assembly.
Sparky,
I have 2004 trailblazer ext with auto AC control and adj gas pedal. have same issue with no dash vents working, ordering new accuater.
Also cold air comes out drivers side – heated air on pasenger and sm vents in middle of second row seats. drivers side will change to heat when auto mode temp set above outside temp, so auto seems to work. rear seat seperate control system works fine.
When power is removed and reconnected to start the recalibration the a/c control panel will default to 74 degrees “F”. Do Not adjust it until after the recalibration is complete.
Sparky, I have a 2003 trailblazer with dual auto climate controls. Same issue as the others. Air out of dash vents works once in a while but is random and usually blows out the defrost and floor vents no matter where the mode button is optioned too. I am going to try the disconnect of the battery recalibration first. Does the climate panel need to be turned off and does the mode need to be in a certain position before I disconnect the battery. When the air does come out of the dash vents it still comes out the floor as well no matter what mode.