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. I had the same problem with the driver side blowing heat randomly and in the winter it wouldn’t blow heat at all followed there steps the temp started working correctly but mode stopped on defrost followed steps 3 more times same result so I tried it once more this time I only turned the key to on position without starting engine and worked great can now control everything as desired thank you 2005 GMC YUKON SLT AUTO CLIMATE CONTROL

  2. It is very common for the vacuum actuators to stop working due to a faulty vacuum hose under the hood on the passenger side of the vehicle. If the vacuum supply hose has a problem all of the vacuum actuators stop working at the same time. There is a round plastic ball under the battery tray area. That is the vacuum reservoir. It should have two hoses attached to it. One will be the vacuum source from the engine. The other will be the vacuum supply to the HVAC control head. Normally there will be a short piece of black vacuum hose that will have softened and collapsed. Might even have a hole in it.

  3. I am also curious about the coincidence of the vacuum actuators not working after the battery died. Everywhere I read online said the actuators often had problems after a dead battery or a battery replacement. But you said these kinds of actuators usually don’t die. Is there a good explanation for this?

  4. OK I just realized that all those “wires” coming from the mode switch and going to the vacuum actuators are not wires at all, but are actually tiny vacuum hoses.

    I removed one of the hoses from one of the actuators and tested all the modes and did not feel any vacuum pressure (should I?)

    Similarly, I noticed that two of the colors: brown and black, seem to be exiting the passenger compartment and entering the engine compartment. I assume these are the hoses that should be hooking into the motor to draw vacuum pressure. I disconnected these and again turned on the engine and felt no pressure at all. Does this mean the problem is somewhere in the engine compartment?

    I tried looking for those same black and brown hoses, but they are either very well hidden, or they are covered in another layer of protection. I couldn’t find them.

  5. I googled pics of vacuum actuators and they mostly look like little disc thingies with plastic housings and usually a single electrical connector. I found THREE things similar to this all in the same vicinity of the temperature control actuator under he passenger-side dash.

    But I from a quick examination, I don’t see anything that looks like a vacuum tube coming out of these…

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