The selector knob for the heat and air unit in my Sentra ( the one that directs air from the dash to the floor or defrost) turns but it doesnt change the direction of the air flo

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?

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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).
  
  

http://www.nicoclub.com/FSM/Sentra/2006_Sentra/mtc.pdf Page 39 is the clip

Pick up a Haynes manual. It has helped me a lot! It will give you advice and help walk you through things like removing your dashboard. Mine has helped me SO much! Worth the money to have. I keep mine IN my car. You can also view the manual online through libraries sometimes if you have a library card.

the selector knob or lever uses vacuum from the engine to open and close the doors that direct the air throughout your dash. check for vacuum leaks.

you need to check the control wire is`nt broken most likely come out from flap connection just reconnect and it will work again,check the flap affected for free movement as could be jamming.

THe blend door seems to be stuck. When you change settings from defrost to floor air or, vent, the blend door opens and closes directing the air to the place you want it to go to. I have had some success spraying a lubricating oil such as WD40 under the dash on the blend door. You need to get under the dash with a flashlight to locate it. It looks like a flap. Spray it with a couple of shots of the WD40. Go easy on the spraying as you may be inhaling the fumes. Keep the doors and windows open to minimize the fumes. Wait about 1/2 hour and try the A/C functions. (defrost, floor, vent air)

vent door is stuck open

i had a simmiler problem on my 95 chevy pick up. on mine it would not chg. from floor to defrost, no matter where i put the selector. with mine it was the controls. if you go under solutions for k1500chevy gmc trucks it should tell you what your problem is, or give you an idea whats going on with yours.