HVAC recirc issue

[hexumaz]

2001 1500HD LT, manual AC controls....had the recirc/fresh air actuator making noise so I bought a new ACDelco replacement. Got it put in and door moves with no noise.

 

Now for the issue. If I have it in fresh air mode and the auto headlights are on at start up, it will move and go to fresh air, but once I start driving and the RPMs go up I can hear the sound of the blower change (louder like when its in recirc mode). When I stop at a light I can hear it change back to fresh air and then back to recirc when I start driving again. Mode button light remains on for fresh air.

 

Similarly, if I start it and the auto headlights are on and mode is in fresh air I can hear that its pulling fresh air from outside. If its daytime and the auto headlights turn off, as soon as they click off I hear the recirc door move and the blower sound increase. Mode button stays lit up for fresh air and I can visually see that the door is now in the recirc position.

 

If I activate the recirc button the light stays on recirc and it never does any of the changing with RPM or auto headlights on or off.

 

Any ideas on whats going in or what to look for?

 

 

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[hexumaz]

Bump...anything?


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[sefiroxx]

Auto climate? Temp sensor could be forcing it to recirc to get caught up on cooling.

[hexumaz]

Auto climate? Temp sensor could be forcing it to recirc to get caught up on cooling.

No just manual dials. I figured a sensor of some kind too but can’t find any that mine would be equipped with.


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[hexumaz]

Put a new dorman HVAC control unit in and no change. Still puts itself into recirc even when the unit shows that fresh air is selected. The fact that the auto headlight condition effects it makes me think there is a voltage draw of some kind that makes the actuator change with lights on/off or with acceleration. Thing is driving me nuts but I can’t find any other sensor that would be related to what I am seeing. Everything else works as it should.


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