The middle vent will start blowing hot air when the A/C is on?

2005 GMC SIERRA
155,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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GERONBELL
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When l stop and switch it off and start back it will blow cool again. It’s getting to be ongoing. Started about a month ago. I changed the bottom blend door actuator about 6 years ago, I had a similar problem with the side vents going to hot.
Aug 8, 2022 at 8:40 PM
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STRAILER
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This sounds like a problem with the door actuator mode which is common. What happens is the potentiometer going out inside the actuator which causes the operation problem. Here is a generic guide to help you see what you are getting yourself into with the repair with instructions on how to change it out in the images below:

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

Check out the diagrams (below). Please let us know what happens.
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Aug 9, 2022 at 9:16 AM