GM HVAC air mode actuator problem

ID Status Date Year Make Model Transmission Type A/C Controls Public/Private
#15203 In Progress 2004 Chevrolet Silverado 2500HD LS, 4x4, 6.6L diesel public

I have a 2004 Chevrolet Silverado 2500HD LS, with manual HVAC system. When I use the AC, there is low airflow coming thru the dash vents. I checked the airflow on the defrost and the floor and it seems to be good, I did noticed though that there was significant airflow coming thru the floor vents when I had the mode selector on the dash. I then cycled the mode switch to each position while watching the mode actuator, the actuator was making a creaking sound and the cam was not rotating far enough counter-clockwise to direct the air to the dash vents.
I replaced the air mode actuator, when I powered on the truck and watched the actuator it seemed to calibrate by rotating fully clockwise and counter-clockwise, however when I cycle thru the modes with the selector switch I’m still getting low airflow thru the dash and continue to get air thru the floor vents.


I have few questions for you.

Have you owned the truck for a long time and did the vent control work properly in the past?

Does the new actuator seem to also not travel far enough in the rotation?

Can you provide the part number of the actuator you installed?

Does your truck have a factory floor mounted center console with bucket seats?

Two door or four door truck?

Good Morning,
I’m the second owner of the truck and have only owned for a few months. The airflow from the dash vents seemed low since I’ve owned the truck. I have good airflow from the defrost and the floor. The truck has a aftermarket HVAC control module and the air mode actuator was also aftermarket.

The actuator doesn’t look like its rotating the cam fully to direct the air flow to the dash vents. Before I installed the new actuator I rotated the cam clockwise and counter-clockwise to check if airflow was being diverted to the proper locations and it worked correctly at that time.

The actuator that I used is Dorman 604-121

Yes, I have a factory floor console with bucket seats, I checked the vents on the back of the console and there is hardly any airflow coming thru those vents.

It’s a four door truck.

Thanks, Scott


I know you said you have good air flow at the defrost and the floor vents. Does the airflow get stronger out the defrost when defrost is selected with just a very little flowing through the floor vents? Does the opposite happen when the floor position is selected? Just trying to get a handle on what exactly is not working correctly. There are a lot of variables.

My two initial thoughts were the wrong part number replacement part was installed or one of the door lever pins is not in the correct slot. You seemed to have negated those thoughts with your last reply. The only exception would be if the wrong actuator  was inside the right box.

As a long shot, you may want to go to the passenger end of the dash and disconnect and reconnect the harness connectors then perform a recalibration.

Thanks for your responses.
This weekend I went thru all of the setting for the airflow direction.
Dash – equal airflow between dash and floor
Dash / Floor – most of the airflow is at the floor
Floor – Good airflow, no airflow anywhere else
Defrost / Floor – Equal airflow in both areas
Defrost – Good airflow

I took the new actuator off and checked the door lever pins, all seemed to be in the correct location. I could manual rotate the cam to the counter-clockwise position and get full air flow to the dash vents. I also put the old noisy actuator back on to check to see if it would rotate the cam enough to direst the full airflow to the dash vents and it did not.

I also performed the recalibration as described in a youtube video from Anthony J350 that referred to Sparky’s as his source.

As far as going to the passenger side harness, I’m not sure where you’re referring.

Thanks, Scott


The connectors are located under the end panel on the passenger end of the dash as shown in the following article.

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