Question about 1994 Jeep Grand Cherokee

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Vent selector will not change the air from defrost position

I know that it works off of vacuum but i am not getting any vacuum to the control module

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  • Anonymous Feb 28, 2009

    Where on the engine does the a/c module get it's vacuum?

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You have a vacum leak.

Posted on Feb 28, 2009

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Why wont my 2001 ford windstar blow out of vents ? only on defrost?


Air Flow Control
Air flow control is accomplished in the following manner:
  • Primary control is through the function selector knob , mounted on the heater function selector switch, which is part of the heater control .
  • The function selector knob has the following positions: OFF, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST.
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  • The vacuum selector valve directs source vacuum to various vacuum control motors (18A318) . Refer to the System Airflow Schematic and Vacuum Control Charts.
  • An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the heater blower motor switch (18578) .
  • The position of the function selector knob determines the manner in which the system will operate.
  • Each position of the function selector knob is detented for positive engagement.
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I am unable to move selector switch from any position - something in the internal workings is broken b/c the knob moves but the air vent direction does not change? how does it work? what is the name of the...


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