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2008 Explorer HVAC hiss/vacuum sound

relentless85

Active Member
Joined
January 25, 2015
Messages
78
Reaction score
2
City, State
Oklahoma, OK
Year, Model & Trim Level
2008 Ford Explorer XLT
2008 explorer with manual climate controls. I started hearing a hissing sound coming from what sounds like behind the far right climate control knob that controls what vents the air comes out of. When I turn the knob to the floor position, the air comes out of the defrost vents and I still hear the hissing sound. However when i turn the knob to the dash vents or defrost vents, the hiss sound goes away and air comes out of the correct vents.

Are there vacuum lines that are connected to the rear of the climate control knobs that would be causing this? Or is it the vacuum components behind the glove compartment or the actual climate control knob mechanism broken?

I plan on trying to fix it this weekend. Is there an easy way to remove the trim around the climate control/radio? I have not removed it and don't want to break it!
 


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relentless85

Active Member
Joined
January 25, 2015
Messages
78
Reaction score
2
City, State
Oklahoma, OK
Year, Model & Trim Level
2008 Ford Explorer XLT
Ok, I located the 2 vac lines going through the firewall on the passenger side. I traced them to the round black reservoir and it is not cracked or leaking from what I can tell. Then I traced the lines up to the back of the climate control knobs. I am getting vacuum up at the controls.

When I turn the knob to the floor position to have the air just come out of the floor vents, the air comes out of the floor and the defrost vents. If i turn it to just defrost, the air just comes out of the defrost vents. If I turn the knob to the dash and floor the air comes out of the dash and floor like it should.

So it appears that I am having an issue with getting air to just come out of the floor vent when the knob is set to the floor position. I can't see any kinks or cracks in the vac lines that run to the control knobs and I check the lines going to the round metal valve things that are in various places behind the dash.

Any suggestion on why I am getting air coming out of defrost and floor when the knob is in the floor position?
 




garye

Active Member
Joined
August 11, 2004
Messages
53
Reaction score
1
City, State
des moines iowa
Year, Model & Trim Level
2008 eddie bauer
I think it is normal for some air to come out the deforst when in floor position
 




relentless85

Active Member
Joined
January 25, 2015
Messages
78
Reaction score
2
City, State
Oklahoma, OK
Year, Model & Trim Level
2008 Ford Explorer XLT
Hmm... There is a lot of air that comes out of the defrost when the knob is on the floor position. Could this be a blend door issue?
 




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