Another HVAC POST

[zmusclow]

So I have been searching and have not found this issue. I have a 2002 Tahoe with automatic AC controls. I replaced the mode door actuator and it was working, but would not fully go to defrost or the upper setting (would be always blowing some out of the feet vent). I just tried to do the actuator calibration. I pulled the fuse for 3 min, reinstalled the fuse and turned key on for 2 min, key off for 15 seconds and key on to test. Now my mode door actuator is stuck on full defrost no matter what setting I have it on. It appears that the actuator went past the range marks while it was installed. Am I doing the calibration wrong or is a Tech 2 needed for a proper calibration?


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[UmmScott]

So I have been searching and have not found this issue. I have a 2002 Tahoe with automatic AC controls. I replaced the mode door actuator and it was working, but would not fully go to defrost or the upper setting (would be always blowing some out of the feet vent). I just tried to do the actuator calibration. I pulled the fuse for 3 min, reinstalled the fuse and turned key on for 2 min, key off for 15 seconds and key on to test. Now my mode door actuator is stuck on full defrost no matter what setting I have it on. It appears that the actuator went past the range marks while it was installed. Am I doing the calibration wrong or is a Tech 2 needed for a proper calibration?


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What kind of actuator did you install?

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[zmusclow]

What kind of actuator did you install?

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I installed the AC delco replacement. I also manually reset the actuator by taking the cover off and rotating the motor. When I retried the calibration it just defaulted to full defrost again.


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[UmmScott]

I installed the AC delco replacement. I also manually reset the actuator by taking the cover off and rotating the motor. When I retried the calibration it just defaulted to full defrost again.


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Sounds like there's something wrong with the control head.

When the control heads go bad they make the actuators do weird things.
In my 00 yukon the control head kept cycling the recirculation actuator from open to closed repeatedly with no reason.
Replaced control head and issue went away

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[zmusclow]

Sounds like there's something wrong with the control head.

When the control heads go bad they make the actuators do weird things.
In my 00 yukon the control head kept cycling the recirculation actuator from open to closed repeatedly with no reason.
Replaced control head and issue went away

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Thank you for the info. Junkyard shopping it is


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[Fless]

There can be updated calibrations (firmware) for the HVAC controls for improvement. Can be done using a Tech 2 and TIS2000.

 

[zmusclow]

Update: I got a Tech 2 hooked up to the Tahoe today. I am getting DTC B0248 “Air Flow Control 3 Circuit”, and B3761 “Air Flow Control 3 Feedback Circuit”. It has a brand new AC Delco Mode door actuator. The actuator moves on command from the Tech 2, but on the data screen it shows mode door max and min position as zero. I don’t know if it’s a bad actuator or if the head unit is bad. Any and all input would be appreciated.

Also upon key off and key on after disconnecting ring the tech 2, the mode door actuator defaults back to full defrost


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[UmmScott]

Control head is bad..

Replace control head, problem goes away [emoji106][emoji106]

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[zmusclow]

Control head is bad..

Replace control head, problem goes away [emoji106][emoji106]

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Thank you! I just ordered one


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[UmmScott]

Unless you have an odd ground or wiring issue, I'd definitely replace the control head

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