Stuck on defrost why?

Hello Debbie

Here is a great guide that will show you where the actuator is and how to change it:

https://www.2carpros.com/articles/replace-blend-door-motor

Please let us know what happens.

Cheers, Ken

Good morning.

It sounds like the mode door actuator may not be working. These actuators are common failures.

Roy

https://www.2carpros.com/articles/replace-blend-door-motor

REMOVAL PROCEDURE

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1. Remove the floor air outlet duct extension (1) from the floor duct (2).

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2. Disconnect the electrical connection at the mode actuator (10).

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3. Remove the mode actuator mounting screws from the HVAC module.
4. Remove the mode actuator as an assembly with the actuator cam.

Any update on the actuator?

Roy

Hello,

It sounds like something happened in the installation. Can you remove the actuator and then plug it back in with it unbolted start he car and work the controls to see if it moves? Also, check the air door by moving it by hand.

Here is a guide that can help you.

https://www.2carpros.com/articles/replace-blend-door-motor

Please let us know what happens.

Cheers, Ken

Good morning.

The reason for that is you replaced the wrong actuator. There is one for the blend door for cool and heat and another for the mode door operation.

Roy

REMOVAL PROCEDURE

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

1. Disconnect the negative battery cable.
2. Disconnect the electrical connector to the mode actuator that is located on the left side of the air distribution case.
3. Remove the screws.
4. Remove the adjuster links from the control lever.
5. Remove the mode actuator.
6. Adjust the mode actuator by completing the following steps:
6.1. Connect the electrical connector to the actuator.
6.2. Turn the ignition switch to the RUN position. Allow the self-positioning of the actuator.
6.3. Turn the ignition switch to the OFF position.
6.4. Remove the actuator from the electrical connection.

INSTALLATION PROCEDURE
1. Install the mode actuator.
2. Install the screws.
3. Install the adjuster links to the control lever.
4. Connect the electrical connector.
5. Connect the negative battery cable.
6. Test the circuit operation.

Hi,

Chances are the problem is related to what is called a mode door actuator. The mode door is what directs air flow. Often times, you will hear a ticking or clicking sound from them when they fail. There is a plastic gear in them and the teeth can break preventing from fully functioning.

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What I suggest is to remove and inspect it. See if it moves when you switch air flow direction. If you find it is bad, here are the directions for replacement. The attached pics correlate with the directions.

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1997 Chevy Truck K 1500 Truck 4WD V8-5.7L VIN R
Mode Actuator
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Procedures With Air Conditioner Only Mode Actuator
MODE ACTUATOR
Mode Actuator Location

Pic 1

Mode Actuator Replacement

Pic 2

Remove or Disconnect
1. Negative battery cable.
2. Electrical connector.
3. Screws.
4. Adjuster links from control lever.
5. Mode actuator.

Adjust
A. Electrical connector to the actuator.
B. Turn the ignition key to the run position and let the actuator position itself.
C. Turn off the ignition key.
D. Remove the actuator from the electrical connection.

Install or Connect
1. Mode actuator.
2. Screws.
3. Adjuster links to control lever.
4. Electrical connector.
5. Negative battery cable.

- Check circuit operation.

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

Take care,
Joe

Hello, I'm Danny.

Yes, it sounds like you are having an issue with the temperature-defrost actuator. Here is a tutorial showing how to change a blend door actuator which is similar:

https://www.2carpros.com/articles/replace-blend-door-motor

I've attached picture steps below on how to change the temp-defrost actuator for your truck. I've owned 2 K1550's myself a 1997 and a 1989. Attached my pictures below for you. If you are on Facebook there is a group-site for us. Here is the group name-
GMT400.com (88-98 GM full size trucks) Let us know if you have any further questions on this issue. Hope this helps and thanks for using 2CarPros. Happy New Year.

Hello again.

I would leave the A/C off but the defrost on so the actuator can position itself. Keep us updated after the install if you have any further questions on this issue. Did you find the Facebook site I recommended? Hope this helps and thanks again for using 2CarPros.

Danny-

You're welcome!

Let us know how the actuator repair turns out. Thanks again for using 2CarPros and we hope you will use our site again in the future.

Danny-

Hello again.

Since this reply came out as a new question I answered in your latest post about the cylinder head auxiliary temperature sensor. Thanks again for using 2CarPros.

Danny-