Interior heater ac question

94Ford'stang

Member
Nov 7, 2020
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New Albany Indiana
Need help, my 94 gt when running heat through defrost works fine but when I try to switch it to ac or through vents won't switch air flow to them what is the part I need to fix this problem or what might be causing issue? I know I just changed a directional motor on my wife's 2014 explorer for the heat/ac but not sure this old of car has a part like that or what it is called any help is greatly appreciated?
 
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Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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There’s a vac line that runs to the flap that controls whether the air goes to the defrost or the vents. If it slips off, it’s stuck on defrost.

look up the left side of the center dash area. The vac line is yellow on fox cars. You should be able to see it go up the left side and connect to a vacuum canister

if it’s connected, you might not have any source vaccum. There’s a single vac line that goes into the engine bay from the heater core area. You’ll want to check to see if this is seeing vac.

that line runs to the hvac controls which diverts the vacuum as needdd. No electrical is involved here
 

Chythar

15 Year Member
Aug 26, 2004
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On 94 cars, it's a small black vacuum line that leads from the firewall on the passenger side all the way over to a vacuum tree on the driver's fender. If that hose is broken or cracked, the vents won't work. It's a common failure on our cars.
 

KRUISR

Well-Known Member
Apr 16, 2015
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The fox cars have a check valve on the passenger side as well as a vacuum accumulator in the passenger fender well. If the check valve fails can have the same issue.
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Its called a vacuum control valve on rockauto. The line pointing right connects to vacuum tree, the other two, one goes to HVAC, one goes to accumulator.
 
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