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.
2005 yukon with automatic temp controls. Changed the starter and battery. After changing, only blows heat through defrost. Did the recalibration as noted on this page. Works fine for 10 seconds or so, then blows heat out of the front facing vents. Can not get any cold air. Everything worked fine prior to changing battery. Any ideas are greatly appreciated.
After engine swap, mode actuator was stuck in defrost mode. Tried several resets of of the net, none worked. Yours worked first time!!! Truck has two HVAC fuses, one under hood one in cab. 2005 GMC Sierra Crew. You really know your stuff, thanks.
You would need to remove the ECC fuse in the driver’s interior fuse box to begin the recalibration procedure for the rear system. Other than the specific fuse, it is the same procedure as the front system.
There was a typo on the mileage, 103,000 sorry. I checked the passenger side junction block, removed and connected several times to clean up any fretting that may have occurred, and found no other damage. I put a light layer of dielectric grease on the plugins to hopefully prevent any future connection problems. Next I re-calibrated the system and checked the command position versus the actual position and found them to be very close. The A.C. pressure is low according to the scanner so I will address that later. Now I am getting a D.T.C. B3531 from the rear HVAC. The command for the blend door and the actual position are almost identical, but according to the scanner there is no movement of the blend door actuator from 60 to about 78 degrees on the front climate control dial and then I finally get heat. I am wondering since I did not disconnect the battery will I have to calibrate the rear independently from the front, and if so, what is the proper way to go about it.
I am assuming there was a typo on the mileage, an extra zero. The first thing that should be done is to go to the passenger side of the dash and remove the end cap. There you will find several junction block connectors. Remove and reconnect each one several times. Look for corroded or damaged terminals. Correct any problems found. The act of removing and reconnecting several times will clear up what is known as fretting (light corrosion). Perform the calibration again and check the actuator actual positions versus the commanded positions. They should be close now. As far as the a/c goes, checking the refrigerant pressure is usually the first step followed by checking request and command data lines in the HVAC module, PCM and BCM. Refrigerant pressure can be checked in data stream or with gauges.