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 KSO,
About your 2003 Tahoe with vent problems. Yes, it is the same general issue, but it uses a different part. Usually on the full sized trucks you will hear an annoying ticking sound behind the dash around where the driver’s right knee is. I have not done a post on this repair yet. Although it is similar in nature to the smaller trucks, there are more pieces that have to be lined up during installation. Sorry for the late relay. My shop and myself have been wide open with the summer heat.
The air flow through the vent problem on your vehicle is likely due to a disconnected vacuum hose under the hood on the driver’s side near the hinge. There should be a vacuum reservoir there and usually there are vacuum hose problems there. As far as the blower itself, locate the blower resistor and check for constant power on the red wire and switched power on the remaining except for the black. It should have ground.
I have a 1999 Chevy S-10 and the air has always blown through all vents. I started it up yesterday and not air moving at all. Could this be a fuse….no I checked all HVAC fuses listed in the fuse box. Any other ideas?
I have a 2003 Tahoe and the a/c won’t blow from the front vent or the floor vents just the defrost the rear works fine is this the same issue?
Thank you, will give it a shot