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.

 

[MikeH]

Heat gauge is in center. Same as my wife’s Liberty (hers blows much hotter). I did back flush the core but I’ll do it again. I’ll try changing out the coolant.

I do not have a recirculate option on the dials except for AC. I did drive around with the dash apart and did not see or feel outside air coming in.

I cut the bottom bump off the blend door shaft and used a scope camera and can see the rotation of the door inside the heater box as I move from cold to hot. If it wasn’t moving I was planning to do a hack I found of manually moving it for the season.

Also considering trying to find a thermostat that has a slightly higher temp range. Is that a possibility? Normally I just get whatever is standard.

 

[KJowner]

Recycle is where mine sits when it's cold, the AC keeps the windows dry and clear.

 

[JeepJeepster]

Heat gauge is in center. Same as my wife’s Liberty (hers blows much hotter). I did back flush the core but I’ll do it again. I’ll try changing out the coolant.

I do not have a recirculate option on the dials except for AC. I did drive around with the dash apart and did not see or feel outside air coming in.

I cut the bottom bump off the blend door shaft and used a scope camera and can see the rotation of the door inside the heater box as I move from cold to hot. If it wasn’t moving I was planning to do a hack I found of manually moving it for the season.

Also considering trying to find a thermostat that has a slightly higher temp range. Is that a possibility? Normally I just get whatever is standard.

Ive never needed to put my KJ in recirculate to help with interior heat. My KJ actually has the best heat and A/C of any vehicle Ive ever driven.

If both heater hoses are hot, then you either have a plugged heater core or the blend door isnt moving as it should be. Make sure you check the temp of the heater hoses when the HVAC fan is on high and the temp is set to the hottest position.