Front vents have stopped blowing in all functions modes

BILLY CARTER

MEMBER
2004 CHEVROLET TRAILBLAZER
4.2L
6 CYL
2WD
210,000 MILES

The back vents are still working fine. I can hear the blower running and feel a little bit of air at the front vents but not working properly I have located the actuators under the dash on drive side and I think that is the problem but not sure which one is the problem. The lower actuator has movement and the top didn't when I went through the modes. Then they did. Not sure if was a full range of motion. Thank you in advance for any you could give.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,706 POSTS

Welcome to 2CarPros.

When air flow directions is not working, chances are it is the mode door actuator. That actuator is responsible for where the air comes out from the vehicle.

Here are the directions for replacing that actuator. I am giving the directions for replacement, but the pictures should help you locate the actuator and confirm it isn't working. The pictures attached correlate with the directions.

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2004 Chevy Truck TrailBlazer 2WD L6-4.2L VIN S
Mode Actuator Replacement

Removal Procedure

1. Remove the left side sound insulator screws.
2. Remove the left hand floor duct. Refer to Floor Air Outlet Duct Replacement - Left Side See: Air Duct > Procedures.

Pic 1

3. Disconnect the electrical connector from the mode actuator.
4. Remove the screws from the mode actuator (1).
5. Remove the mode actuator.

Installation Procedure

pic 2

Important: The new actuator is in Bi-Level mode. Place the door in the middle of the travel position before you install the actuator.
1. Install the mode actuator (1).

Notice:

2. Install the screws to the mode actuator (1).

Tighten
Tighten the screws to 1.9 Nm (18 lb in).

3. Install the left hand floor duct. Refer to Floor Air Outlet Duct Replacement - Left Side See: Air Duct > Procedures.
4. Install the left side sound insulator screws.
5. Recalibrate the mode actuator. Refer to Actuator Recalibration See: Heating and Air Conditioning > Programming and Relearning.

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If you replace the actuator, here are the directions for recalibration. The manual recommends the use of a scan tool to do this, but it can be done without. I will supply the directions without the tool.

Alternate Method (w/o Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch to the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Remove the HVAC B fuse for a minimum of 10 seconds.
6. Install the HVAC B fuse.
7. Start the vehicle.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

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Let me know if this helps or if you have other questions.

Take care,
Joe

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