What does this plunger valve thing do?

[MikeH]

2004 Jeep Liberty Renegade. I’m trying to figure out why my heat isn’t as hot this year. Flushed core so now tore apart half of dash to check components. Actuator motor makes noise and seems to be fine. Switches cold to warm. Can’t tell if moves flap inside as far as it should or not. Anyway I noticed this plunger thing behind the glove box that opens a flapper door. What is it for? When does it open the flapper? Brings in outside air? Maybe it’s opening and mixing in cold air?

 

[JeepJeepster]

That does appear to be the 'fresh air' door. No, that will not cause the heat to not be as hot.

 

[MikeH]

That does appear to be the 'fresh air' door. No, that will not cause the heat to not be as hot.

Do you know when it opens? What activates it to open?

 

[KJowner]

I think it's open in all positions except recycle - knob fully turned to the left.
In really cold weather I find that's the hottest setting but needs the AC running or whole truck steams up.

Is your temperature gauge sitting in the middle when you go for a drive? A cool engine won't heat the cabin well.

 

[budget76]

my 2 cents. I also needed to flush the heater core . now time to change engine coolant as is old. no advise other than stuff in heater box leaves squirrels.

 

[JeepJeepster]

Do you know when it opens? What activates it to open?

Its a vacuum actuator and it will be closed when you have the position knob on recirculate and will be open (pulling air from outside) on all other positions.