What is the likely cause for the vent selector not to switch over to change from heater to defrost etc.?

Vent Type Selector Not Working - Jeep Wrangler Forum

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Oct 13, 2011 - 30 posts - ‎21 authors
It will not switch into upper vent mode, only have the option to have it all on my ...You mean the switch itself on the dash will not turn physically?

Turning vent knob (defrost, mix, dash,floor,etc.) has no - Fixya

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Turning vent knob (defrost, mix, dash,floor,etc.) has no effect. Posted by Jim Long on Jan 01, 2016. Want Answer 1. Clicking this will make more experts see the ...

a/c problem fixed - ChevyTalk - FREE Restoration and Repair Help ...

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3) Mode of operation knob has no effect (air comes only to floor for example) 4) Rear defog ... The transistor is MPSA56 (bipolar pnp) and you can locate the faulty one easily. It is the .... With the switch turned only to Vent, no air from anywhere?

Climate vent knob not working [Archive] - VW GTI Forum / VW Rabbit ...

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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.
• The heater function selector switch combines a vacuum selector valve with an internal electrical switch.

• 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.
• You probably have a vacuum leak , Pull heater control panel an check for vacuum . A broke vacuum hose or The vacuum selector valve is bad ! Or check for a vacuum hose in the engine compartment being off somewhere !
  

. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ?
Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
• The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
• Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and 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.
• Vacuum Control Motors The vacuum control motors (18A318):
  
  • are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
  • direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
  • The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).
  
  

sounds like you have a vacuum line off so your vent doors will not be able to move

defrost is the defalt mode look for a damaged vacuum line going ti the control head

Your selector is controlled either my linkage or pressure tubes. A common problem is for a crack to develop in the hoses and leak the pressure needed to switch to the desired setting. Inspect the hoses and or linkage. that will solve it

Here is the info. I hope the pictures show up. please rate assistance. thx.

Air distribution within the vehicle is determined by the function selector switch position. Two airflow mode doors are used to direct airflow within the heater core and evaporator core housing. The function selector switch/cable assembly is used to position these airflow mode doors. Refer to Section 412-00 for description and operation of each of the system functions.
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Function Selector Cable Assembly
The function selector cable assembly moves the airflow mode doors to the desired position using a 2-sided pull-pull type cable assembly. The function selector controls the cable movement. The end of the cable assembly attaches to the airflow mode door/temperature blend door actuating assembly which transfers the cable movement to the 2 airflow mode doors.
An electrical switch is incorporated into the function selector to notify the A/C switch assembly if DEFROST or FLOOR/DEFROST is selected. When DEFROST or FLOOR/DEFROST is selected, the A/C switch assembly will disable the RECIRC request button and send an A/C request to the powertrain control module (PCM) regardless of the A/C request button indicator ON/OFF status.
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SECTION 412-01: Climate Control 2005 Focus Workshop Manual REMOVAL AND INSTALLATION Procedure revision date: 02/25/2004
Function Selector Switch Printable View (173 KB) Removal and Installation

1. Remove the 4 bolts and position aside the lower steering column cover.

1. Remove the function selector knob.

1. Remove the center instrument panel finish panel.
   • Disconnect the cigar lighter electrical connector.

1. Detach the function selector switch.
   1. Disconnect the electrical connector.
   1. Remove the screw and detach the function selector switch.

1. Detach the function selector cable and remove the function selector switch/cable assembly.

1. To install, reverse the removal procedure.

could be ur selector switch or heater control mod

U have either lost the vacuum to the mode selector switch (in the dash control) or the vacuum mode selector switch is leaking in the ac/heater control in the dash, u can usually hear a hiss if it is leaking. the vacuum source is the engine, a small hose runs through the firewall on the passenger side to the switch from the eng vacuum source.

Yes it could be the switch but you should be able to reach up under the dash and manually switch the vents by hand