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. It sound like you have adjustable pedals and that makes it much more difficult. I had someone state that they could do it without taking the accelerator pedal assembly out but to the best of my knowledge it has to come out. Unless your arms are thin and very flexible.

  2. Sparky,

    I have a 2005 Trailblazer 4×4 LT. There is more stuff attached than the picture you showed, but the big problem is the vent tube. There is no way to get it out. It is U shaped and hooked to another vent on top. I disconnected it from the top, but it wraps around the throttle assembly and is impossible to get out. And there is no way to get my hand in there without that removed. Any suggestions?

  3. If it will get hotter on the driver’s side when switched to full heat the system may be low on refrigerant. If it stays the same temperature when the temperature is adjusted the driver’s temperature door actuator is likely to be stuck.

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