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2008 Explorer hvac won’t go to floor setting

relentless85

Active Member
Joined
January 25, 2015
Messages
79
Reaction score
2
City, State
Oklahoma, OK
Year, Model & Trim Level
2008 Ford Explorer XLT
2008 Ford Explorer 4.0L. When I turn the hvac knob to change it to where the air is supposed to come out the floor, the air comes out of the defrost position in the dash.

I know that is the “default” location the air comes out if the hvac system looses vacuum.

So I don’t know where to start looking for the vacuum leak or what parts to replace. I know a few years ago I replaced a check valve in the engine compartment that had to do with the hvac system but it did not fix it.

When I am driving, I hear a hiss sound coming from the black resivour that is under the passenger side dash area. The hiss is more pronounced when I am giving the engine gas and increasing in rpm. The resivour does not appear to the cracked.

The control knobs on the dash have a little crack near the air location selector knob, could I be loosing vacuum there?

Is there a diagram somewhere I could look at to see where the vacuum lines run and what the part numbers are for the lines, check valves, resivour and control knob module?
 




relentless85

Active Member
Joined
January 25, 2015
Messages
79
Reaction score
2
City, State
Oklahoma, OK
Year, Model & Trim Level
2008 Ford Explorer XLT
2008 Ford Explorer 4.0L. When I turn the hvac knob to change it to where the air is supposed to come out the floor, the air comes out of the defrost position in the dash.

I know that is the “default” location the air comes out if the hvac system looses vacuum.

So I don’t know where to start looking for the vacuum leak or what parts to replace. I know a few years ago I replaced a check valve in the engine compartment that had to do with the hvac system but it did not fix it.

When I am driving, I hear a hiss sound coming from the black resivour that is under the passenger side dash area. The hiss is more pronounced when I am giving the engine gas and increasing in rpm. The resivour does not appear to the cracked.

The control knobs on the dash have a little crack near the air location selector knob, could I be loosing vacuum there?

Is there a diagram somewhere I could look at to see where the vacuum lines run and what the part numbers are for the lines, check valves, resivour and control knob module?
Also I noticed yesterday that sometimes when I’m giving the engine more gas than usual, say to merge onto the highway, the air will go to defrost location for a few seconds then return to the dash vents.
 




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