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.
Sparky,
I have an 04 silverado 1500 and for about a week my truck was barely starting/holding a charge. I deduced that something was drawing power while the vehicle was off. After connecting a test light to my battery cable, and pulling the fuses one by one to try and find the draw, I came up empty handed. I did however pull this code B0263 and am having the same issues as all these folks with the hvac not working properly. Is this part what was drawing power from my battery the whole time? Where would you go from here?
WOW! 10 minutes…..You sir are a genius!!Thanks a million!
Your vent problem will be the same as everyone else. The stalling problem is related to the battery disconnect issue as well. This is what likely happened. The computer system compensates for carbon build up on the throttle plate as it occurs, learned memory. When you disconnect the battery that learned memory is gone and the computer thinks that the throttle plate is brand new and clean again. It is not though. The computer system will relearn, in time and the stalling will go away. To correct the problem sooner rather than later the throttle plate needs to be cleaned. Most parts stores carry throttle plate cleaner in spray cans if you want to do the cleaning yourself. Do Not spray the cleaner into the throttle body. It will be damaged. Spray it onto a rag. Make sure the key is off. Open the throttle plate with a screwdriver handle or stick and rub the throttle plate and bore until clean. You will want to use protective gloves as well. The chemical can feel quite uncomfortable
I have a very similar issue. Most like a few on top of each other. Replaced the battery in my 04 trailblazer, now as others, no air coming out of the front vents, *ALSO* when I turn on the heat to defrost the engine cuts out. This was not an issue before changing the battery. Just wondering if the two are related being as they both started right after changing the battery. I thank you in advance. Great Site!
It is part number 15-73952 and is available at the following address. You will need to copy and paste the address.
http://store.the-electric-connection.com/Product581
It is located under the driver’s side of the dash. On the end of the a/c box. It has a large flat gear assembly attached and takes a little patience and coordination to replace.