2004 Chevrolet Trailblazer, Identifying Heater A/C Actuators

This 2004 Chevrolet Trailblazer came in with the air flow stuck coming out of the defroster. I have already done a post on how to replace the faulty mode actuator, but I did not have a good enough picture to identify all of the actuators on the driver’s side of the dash. To see that post please click here. The view below shows the three actuators and is taken from the perspective of the driver’s feet, looking above the accelerator pedal and towards the center of the dash.

If you click on the picture it will enlarge to show more detail. This layout generally applies to 2003, 2004, 2005 2006, 2007, 2008 and 2009 Chevrolet Trailblazer and GMC Envoy.  It also applies to Buick Rainier, Isuzu Ascender, Oldsmobile Bravada, Saab 9-7X and Chevy SSR. This second group of vehicles, of course did not exist, during all years between 2003-2009.

Once the mode actuator is removed and the new one is ready to be installed, you will need to locate the indexing pin as shown in the picture below. That pin slides into the notch on the white gear on the actuator.

I slide the new actuator into place with the notch and pin aligned and then rotate the actuator slightly to align the mounting holes.

The actuator on the right is the new actuator and the indexing slot is clearly marked. Please click on the picture to enlarge for a better view. The picture also shows the over traveled (stuck) position of the old actuator.

If you would like to purchase the Mode Valve Actuator (part # 15-73596), you can do so by clicking here.

44 discussions on “2004 Chevrolet Trailblazer, Identifying Heater A/C Actuators”

  1. I have never heard of an issue as you have described it. Start from the very beginning and tell me how everything started and what has been done. I need part numbers off of the old part and the new replacement actuator part number.

  2. I don’t remember which way the air was flowing but the white part moved so far down that I could move the direction of the air with my fingers my moving the part where the actuator was supposed to connected to. I’m not sure why it went so far out of position.

  3. I’ve got a 2004 Trailblazer and when I put the new actuator in with the guide pin lined up the actuator rotates clockwise all the way until the white part is pointing to the 4-5 O’clock position. It completely rotates out of contact with the gear that operates the vents. I’ve put it in twice now and it does the same thing. Must be something else wrong.

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