How to Replace the Mode Actuator on Trailblazer

Remove the screws that secure the lower sound insulator to the driver-side dash, using a socket and ratchet. Lower the panel and remove it. Follow the floor duct to the heating, ventilation and air conditioning case. Remove the pushpin retainers, then pull the duct off the HVAC case.

Disconnect the wiring harness from the mode door actuator -- the mode door actuator has a white gear extending from one side and is the lower of the two actuators.

Remove the screws from the actuator. Pull the actuator from the HVAC case.

Rotate the white gear on a new actuator to match the position of the gear on the old one. Install the actuator and tighten the screws to 18 inch-pounds, using a torque wrench. Connect the wiring harness.

Press the floor duct into the HVAC case, then install the pushpin retainer. Install the lower sound insulator panel and snug the screws.

Access the rear fuse box and remove the fuse No. 36 labeled "HVAC B." This fuse is the third from the bottom, on the far left. Wait 10 seconds, then install the fuse. Start the engine and wait at least 40 seconds for the HVAC system to calibrate before adjusting the heater controls.

Look at the forward-facing side of the shifter knob and find the knob set screw. Remove the screw with a T-15 Torx driver. Squeeze around the base of the shift boot, then lift the boot off the center console. Disconnect the wiring connector from the shift knob. Remove the knob and boot as one piece.

Lift the armrest and remove the rubber mats from inside the storage bin. Remove the six bin-retaining screws with a Phillips screwdriver. Remove the bin from the console to reveal the two console mounting bolts.

Remove the two console mounting bolts. Lift the parking brake so that it is fully engaged. Slide the console rearward. Raise the rear of the console, then disconnect the wiring connectors. Lower the parking brake handle half way, then lift the center console and remove it through either rear door.

Remove the screw for the rear outlet duct, then remove the duct. Disconnect the wiring connector from the actuator. Remove the actuator screws, then pull the actuator away from the HVAC case.

Install a new actuator to the case and tighten the screws to 17 inch-pounds. Install the rear outlet duct and snug the screw. Guide the center console into your trailblazer and into position. Lift the parking brake to the fully engaged position. Connect the wiring connectors, and slide the console forward. Install the console bolts, then tighten them to 22 inch-pounds.

Lower the storage bin into the console. Install the retaining screws and snug them. Place the rubber mats into the storage bin. Lower the parking brake.

Lower the boot and shift knob onto the shifter. Install the knob set screw and snug it. Push downward on the base of the boot to secure it.

Remove fuse No. 36, labeled "HVAC B" -- third from the bottom, on the far left --from the rear fuse box. Wait 10 seconds, then reinstall the fuse. Start the engine and wait at least 40 seconds before adjusting the heater controls.