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No heat and the vent switch doesn't work

Drakefitz

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Richmond, ky
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1998 mountaineer
Hey guys, I just bought a 1998 mercury mountaineer with the v8 awd yesterday and the guy told me about the blend door issue but the vent selector switch is stuck on defrost. I'm not familiar with how the climate control system works on this vehicle and was looking for some pointers and tips on what might be causing my issues.
 


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koda2000

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Do you have the automatic or manual HVAC controls? Typically when the air only comes out the defroster vents you have a vacuum leak (or broken vacuum hose). DEFROST is the default setting when your controls have no vacuum.
 




Drakefitz

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1998 mountaineer
Do you have the automatic or manual HVAC controls? Typically when the air only comes out the defroster vents you have a vacuum leak (or broken vacuum hose). DEFROST is the default setting when your controls have no vacuum.


I have the manual controls. Where would I look for leaks at? Where are the most likely to happen?
 




koda2000

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I have the manual controls. Where would I look for leaks at? Where are the most likely to happen?

There's a small plastic vacuum line on the passenger side of the engine compartment that goes from the intake manifold to the the vacuum ball/reservouir located in the front of the passenger side fender attached to the top of the plastic inner fender. Then there's a second vacuum line that goes up to the firewall and then goes to the HVAC control. A disconnected/broken line anywhere (or a vacuum leak anywhere) will cause the same problem. Happy hunting.
 




Turdle

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