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.


*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.

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

  1. Hello. I have a 2003 Tahoe z71. The front AC works fine. It’s a digital one and it has the abilities to go from hot to cold and also change settings from feet to head.

    However, my rear AC is a different story. On the rear AC, I have the capability to change the fan settings along with changing the amount of air is pushed between the head and feet just fine. The temperature setting between hot and cold, I am unable to change. The temperature it’s not blowing hot, neither it’s blowing cold. It seems as if the compressor is not working, however it is as the front AC works just fine. What can it be? Thanks.

    1. The front and rear systems share the same compressor. I would recommend the following. Start the engine and run the a/c for several minutes. Open the hood and locate the a/c suction lines on the passenger side of the vehicle. The main suction line will be attached to the accumulator tank. follow it back to locate the “Y” that goes to the rear of the vehicle. All three legs of the “Y” should be equally cold and sweating. Next, confirm the transmission shifter is fully in park. Set the parking brake and chock the rear wheel against rearward movement. Lay on the ground parallel to the side of the vehicle at the passenger rear of the vehicle. Locate the a/c lines(one small and one large). The larger line should be cold and sweating. The small one should be warm/hot(use a light quick touch at first to confirm it will not burn you). If all of that tests as okay you likely have a problem with the rear temperature blend door actuator. If the rear suction line is not cold and sweating then either the refrigerant charge is low or the rear expansion valve is faulty/blocked. However, I do not recommend just trying to top off the refrigerant system as a test. The refrigerant charge level has to be accurate to work properly and this can only be done by measuring the refrigerant weight.

          1. Thank you for the knowledgeable information and swift reply. I will do what you advise and will report findings!

  2. The rear air system in my 2004 Chevy Suburban 1500 LT is blowing warm/hot on the max cold AC setting (driver’s rear controls by rear view mirror set to auto blower/max cold temp/auto bilevel). The blower and the bilevel seem to be working just fine. With the rear air blowing warm/hot on the max cold temp setting (overhead driver’s rear controls), I can change the temp setting to max hot and, over the span of about 10-15 second the air will blow hot to warm to “cool” then back to hot. That suggests to me that the actuator might be working and is just out of calibration.

    My main question is – does Sparky’s actuator calibration procedure work for the rear air system, as well? Do I need to do anything special to get the rear system to calibrate? After multiple calibration attempts using the above procedure, I don’t get any change on the rear system (although I did somehow get the front to blow hot and had to do multiple attempts just to get things back to where I started).

    Thanks …

    1. GM does not list a recalibration procedure for the rear system. If you wanted to try something you could do the procedure you have already tried but using the ECC fuse in the interior fuse box instead of the fuse listed in the article. Most likely you will need to replace the faulty actuator.

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