HVAC Actuator Recalibration Procedure For GM Trucks and SUVs

The topic of how to perform the actuator recalibration procedure on Chevrolet , GMC and Cadillac Trucks and SUVs has become an ever increasing topic of discussion.

For manual systems it does not matter where the a/c controls are set but if you feel the need to do something, turn the blower switch on (I prefer speed 3) and set the temperature sliders about .5″ to .75″ from full cold.

For auto systems, press the auto button, with the key on.

Turn the ignition off.

Remove the HVAC/ECAS , 10 amp fuse in the underhood fuse box* or disconnect the battery for one minute.

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*Fuse locations can vary from year to year and between different models. Hopefully I will be able to build a list for this.

Install the HVAC fuse or reconnect the battery.

Start the engine. On systems with auto a/c controls the controls will default to 74 degrees F when the ignition is turned back on.

DO NOT TOUCH the a/c controls.

Let the engine run for 1-2 minutes.
Turn the ignition off for at least 10 seconds but no more than 30 seconds.
Restart the engine and then test the a/c controls.

301 discussions on “HVAC Actuator Recalibration Procedure For GM Trucks and SUVs”

  1. 2005 Yukon XL Denali with electronic controls. Performed HVAC recalibration because recirculate door is stuck in the opened position. Recirculate door goes through full motion (open/close) after reset but comes back to open and does not function. I’ve unplugged climate controls and let it sit for 15 minutes to no avail. Goes through the same cycle and stays open.

      1. Does the LED on the recirculation flash when it is depressed? If so you may want to look at ambient and interior temperature sensors. If the computer thinks it is too cold it will only allow fresh air operation..

        1. Hi Sparky,

          No it does not flash when depressed. Light stays solid. I was able to get my hands on a cheap scanner and I’m pulling code B0229 which indicates a issue with that actuator. I have performed the reset a bunch of times and the door still cycles open and closed but will not function afterwards. Doesn’t seem like a issue with the actuator itself?

          1. Actually it does seem like an actuator fault. The thing that happens during the recalibration is that the actuator is commanded to move while the control panel monitors feedback voltage to identify the actuator position. If the wrong voltages are seen the control panel goes into default or fail safe mode and stalls the actuator.

  2. I have a 07 Silverado. I’ve replaced the mode actuator but it still comes out of the defrost. If I change the setting it comes out of the front vents for a moment and then back to defrost. I’ve checked and I can see the actuator moving. Any ideas why it’s doing this?

    1. I’m having the same issue with my 04 Avalanche. Replaced the mode door actuator down by and above the gas pedal area and it does cycle through all of the modes but ends up in the defrost mode after it finishes cycling and then won’t respond to the controls. Not sure what to do from here.

      1. There are a few things that could be going on. Number one check to make sure that the correct part number replacement part was installed. Second make sure that it is properly installed. Improper alignment can cause a fault code which in turn may force the actuator to the default defrost position. Also poor connections at the actuator, passenger side junction block or control panel could cause a fault and drive the system to default mode. It is best to check the operation with a compatible scan tool.

  3. I have a fun one. 2004 gmc 2500hd crew cab auto hvac. New control panel, new blower resistor, new harness. When I do the calibration it comes on. You can here it move the actuators. The blower motor display will go up some then it goes all the way down. The blower motor never turns on. Bypass and apply direct power thru the blower resistor harness and the motor works. No codes for anything hvac just ddr module and an onstar antenna code. Any thoughts?

    1. Sounds like there is no power on the red (input) wire at the blower speed controller (resistor). The two common causes would be a blown BLWR fuse in the under hood fuse box or a damaged terminal under the fuse box for that circuit.

        1. That pretty much leaves a problem on the small purple/white control wire or one of the new parts is faulty. What was the part number of the new blower speed controller (resistor) and what color is it?

          1. It’s just a standard ru631

            I’ve rechecked the part number and have replaced the control panel again. What voltage should the signal have?

          3. Thanks! I went to start checking the signal voltages and got nothing. Traced it back to an open in the signal wire about 6″ behind the control panel.

  4. Hi Sparky, I’ve tried this procedure on my 2002 Trailblazer with Manuel controls. Both removing the fuses and disconnecting the battery. I still have hot air only blowing from both driver and passenger sides. Through the glove box I can see the actuator not turning for the blend. Seems odd to me that both would go bad at the same time. Does the reset work on a 2002? Thank you

    1. To perform the recalibration procedure on your vehicle you need to start by removing the HVAC B fuse in the rear fuse box. Then proceed as outlined in the recalibration articles. Something else you should know is that the Trailblazers and Envoys are prone to having one actuator fail and locking the whole system down. It is easier to identify any faulty actuators with a system compatible scan tool. The far harder method is to physically look at each actuator one at a time while someone else performs the recalibration process. Hopefully you can see which one fails to move correctly.

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