Blower vent selector switch not working. Only works in defroster position

It could be something as simple as a blown fuse or the blower speed switch is bad.

I would first check the fuse for power with the key on. Check both sides to make sure it's at least receiving power. You can use a cheap tester that lights up for the check.

IF the fuse checks OK then it's time to check the blower switch or make sure the heater selector isn't in the "OFF" position.

On some GM vehicle the heater control selector that lets you adjust from floor, to defrost, to dash vents, etc. has an "OFF" position when the selector is adjusted to the far left.

Without physically being there to actually look at it, these are the only suggestions I can come up with.

Hope this helps.

How to fix (unstick) a stuck fan vent selector on a Toyota ...

? 2:04
https://www.youtube.com/watch?v=a0JDRbCgDw0
Jan 17, 2014 - Uploaded by RodneyDickson
In this example, my 2001 Toyota Echo had its fan vent selectorindicator stuck in one position of the dial ...

Car fan / AC only works on high - Replacing the Blower ...

? 4:24
https://www.youtube.com/watch?v=33fqw0k_qkM
Aug 4, 2011 - Uploaded by Laiwah Manh
The fan in your car stopped working except when set to the highest setting. ... Sign in to make your opinion ...

03 jeep grand Cherokee blows out defrost only - Yo

The selection door, is operated by 1/4" vacuum hoses. When turning the knob or sliding a lever, to select between floor, vents, or dash deck for windshield defrost, vacuum is created by the valve body and the blower will then blow thru the desired vents. When these hoses/lines are compromised, especially on a vehicle over 15 years old it seems likely, vacuum won't be created, and the last working position, is normally where it stays! Until the lines are replaced.
Good luck.

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).
  
  

Hey man if the blower is working and air is coming from your other vents i have a few ideas.First i would start by checking your vent selection switch something may be stuck where the dash vents open. If the selector is fine you should try checking the ducting behind the dash it could have come apart or simply be cloged where it routes air to your dash. hope that is helpfull.

check your blower hoses to see if one or more have come loose or got redirected or the selector switch isn't functioning properly (is it blowing better on defrost as opposed to floor vents, or forward vents, etc.)
Good luck

sounds like it is vacume operated check to see if all vacume hoses are connected to the control switches and vent controls. i suspect somebody has caused a hose to disconnect tampering under the dash

I have the same problem. I've heard the ignition switch harness is shorting out and replacing the ignition switch ($75-$125 part) will fix it. A few torx drivers and sockets are needed to replace it (a 4mm hex socket works for the column covers, but the bolts holding the ignition switch in are even smaller. I have it apart down to where I need a smaller torx socket to continue.)

THE DEFROSTER DOOR WAS FROZEN SHUT. WHICH CAUSED COMPUTER SWITCH TO GO OUT.HAD TO REPLACE THE DEFROSTER BOX(?) AND COMPUTER SWITCH. WORKS FINE NOW.