Why does my ac blow only through heater & defros vents

"The actuator isn't working. You should be able to manually move it, assuming you can see it from the passenger side, under the dash.

The cause can be mechanical binding or something is jammed in there to prevent it from moving.

The other possibility is that the selector control isn't working. Sometimes, disconnecting then reconnecting it will solve the problem. You should be able to find instructions to disassemble this on the internet."