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.
The repair for your blower issue is not hard but you do need some basic tools. Sockets, ratchet, wire cutters, strippers and crimpers. The repair can be found at the following post link address. You will need to copy and paste the address into your browsers address bar.
http://www.sparkys-answers.com/2010/02/2006-chevrolet-trailblazer-blower-inop.html
i am mechanically illiterate – i have a 2004 tralblazer LS 6 cyl – heat knob has to be at 4 or 5 to work; 3 stopped working today, and 1 and 2 last year. what do i need to do to avoid taking out a bank loan to pay for this repair?
I guess that would depend on just what the problem is? Could you give some more details about your situation?
I just changed the battery in my 03′ Envoy XL. There’s no digital read out for the dual temp controls. Is the actuator the cause of the problem?
You really should use an amp meter to test for a drain due to module sleep times. If you do find yourself having to use a test light, you will have to do this. Disconnect the negative battery cable and hook your test light in between as you normally would. Next connect a parallel jumper wire to the test light ends. Turn something on to make sure your jumper wire and test light have a good connection. Then turn that load off and wait one hour. Leaving the test light in place, remove one end of the jumper wire. If the test light is illuminated, you have a drain. If it is not illuminated more than likely your battery is faulty. The B0263 of course would be the reason why you do not have vent control but it is an ignition controlled circuit. It would be unlikely to be the cause of your drain.