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 is highly likely that this is your problem, particularly if the battery has been disconnected recently. I do however recommend inspecting and testing if possible.
Ok, so air is not blowing out of the front dash vents in my 2003 Trailblazer. The back controls work fine. Think this is the actuator? Air isn’t blowing regardless of whether the a/c is on or off. Help!
If the blower works on all speeds but the air only comes out of the defrost and the floor, then the mode actuator is likely to be faulty. If the blower does not work or does not work on all speeds then the resistor and harness connector are likely to be the problem. If you have both symptoms then you have both problems.
I am having the same problem in my Trailblazer. Some sites suggest that a new blower motor resistor is needed. How can I tell if I need a new actuator or a new blower motor resistor?
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.