1996 gmc vent position wont change

[454ss]

1996 yukon wont go to bi-level for thr bair conditioning, it will go from defrost to the floor but not in between, what controls this, is it a switch that went bad?

[454ss]

somebody has to have knowledge about this, dont they?

[97C1500&84Z28]

somebody has to have knowledge about this, dont they?

 

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Same thing happened with my wife's Astro van. Turned out to be the vacuum line that operates the switching of the vent became disconnected. Simple fix.

[99-2door]

There are no vacuum lines on a 96 Yukon's HVAC system.

 

The most likely culprits are the actuator or the linkage for the AC box doors. Look under the dash near the middle on the far left end of the black AC box. There is a electric actuator motor that is attached to some linkage rods. Take the 2 or 3 screws off the motor and pull it off. Once you have it loose turn on your AC fan and then move the linkage with your hand. It has several positions that correspond to the various combinations of defrost- dash vents and floor positions. If you can move the linkage and make everything work properly then your SC box is fine. If not, checl the linkage to make sure it isn't binding. Now adjust the postion on the AC controller and watch the actuator to see if it moves when it should.

If all these things check out, then you have a problem inside the box. Which means dash removal..... BOOO