Will not change settings from blowing through the defrost vents?

SIMRIG32

MEMBER
1997 BUICK PARK AVENUE
140,000 MILES

I purchased a brand-new known working mode door actuator and after installing I removed the HVAC fuse to reset the system, when I started the car, the actuator moved all the way to the far-right position which is defrost and never moved from that spot again. I have also since then replaced the climate control head unit with the same result. I have also checked that the vents can be moved by hand without an actuator installed and they work fine. The blend door actuator seems to be working fine also.

7 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

Yep, it sounds like the new mode actuator has a bad potentiometer I would get another one. Here are the instructions on how to change it in case you need them.

Remove or Disconnect

- The actuators are specifically designed for the right and left side of the heater and A/C module. When servicing an actuator, be sure to replace it with the correct service for the position being serviced.

1. Sound insulator(s) as required to gain access to actuators.
2. Knee bolster, console, trim as required.
3. Electrical connector from actuator.
4. Screws retaining actuator.
5. Actuator.

Install or Connect

1. Actuator with mounting screws.

Tighten
- Screws to 1.4 N.M (12 lb. In.).

2. Electrical connector.
3. Knee bolster, console, trim.
4. Sound insulator(s).

Important
- After the actuator has been replaced, the actuator needs to be recalibrated for proper travel. The ignition must be cycled ON for 3 minutes to allow the programmer and the actuators to recalibrate for proper travel.

Check out the images (below). Please let us know what happens.

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Monday, March 20th, 2023 AT 5:03 PM

SIMRIG32

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4 POSTS

Okay, if the original actuator did the same thing but still worked with a 9v battery and the replacement also worked outside of the car is it the actuator that's bad or something else in the system? Is it common for actuators to go out but still move with power outside of the car? Just trying to make sure that it's definitely the actuator and not wiring or something else before I buy a new one.

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Tuesday, March 21st, 2023 AT 10:27 AM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

Did the new actuator and old one do the same thing? If so, you could have a wiring/connection problem, or the HVAC controller is out. Check out this guide to run the wiring test and I have left the HVAC wiring diagrams so you can see how the system works and how to run the tests:

https://www.2carpros.com/articles/how-to-check-wiring

If everything checks out here is how to change the HVAC programmer. Check out the images (below). Please let us know what you find.

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Wednesday, March 22nd, 2023 AT 4:40 PM

SIMRIG32

MEMBER
4 POSTS

I have fixed the issue with the mode door actuator on the driver's side by plugging it into the cable that was originally on the blend door actuator, it seems like someone has been through all the wiring in the car, now the blend door actuator on the driver's side is not changing, it has the same symptoms that the mode door actuator originally had, I suspect the wiring harness to the blend door actuator to be bad, 2 new actuators have been installed and each one travels all the way to the far right position out of range and stays there permanently, what voltages should I be looking for on the harness and if there is an issue how would I go about fixing the problem, thanks for all the help.

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Monday, April 10th, 2023 AT 12:33 PM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

I am glad you figured it out, you are right, the HVAC wiring needs to be in good shape for the system to work. Please let us know if you need anything else to get the problem fixed.