Hey guys, im halfway through swapping out my heater core, question what makes the blend door open and close? whats the purpose of it? When i got in there the blend door was wide open, when i removed it it moves freely and looks fine. just curious

Thanks

 

It's driven by the temperature control switch that sends a signal to the blend door actuator. The purpose of the blend door is to separate heat from a/c.

This is the doors position on cold


This is the doors position on hot