A/c Vents in front are not blowing from the panel but is bowing in the back and the defrost vents? How can we fix this? A/C is working just not blowing from front vents.

In f150 truck there is a small vacum hose passenger side up by the windshield. It's a small hose check really good they dry rot and it will cause your vents to switch. Also if your box is bad. It's next to the battery

I had a similar issue on an 05 silverado. Air would only blow out of defrost vents. But this worked for me:

1) Unplug HVAC fuse for 10-30 seconds
2) Start truck
3) A/C comes out defrost - wait about 10 to 15 secs
4) A/C then starts coming out the floor vents for about 5 seconds
5) A/C then starts coming out the dash vents.
6) While the A/C is coming out the dash vents, turn A/C OFF (otherwise it cycles back to defrost for good).
7) Turn truck OFF
8) Restart truck and it should work fine

(Found solution on another forum from user "ccurran")

I had the AC problem too, and they said there was a hole in the hose. They fixed it and now it comes out of the vents as it suppose too, but when I first accelerate to go up a hill, it stops blowing out of the dash vents. Once I have stopped going up the hill, the air starts blowing out again. Weird.

replace the the heater control panel..real common on gm trucks

had this trouble in a dakota it was a blend door in the heater unit. had to remove entire dash to repair

the deflector flap that move to direct air flow is stuck under the dash.

Try replacing the cabin air filter.

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.

I think it is going to be a vaccum leak.

vents are blocked so air is diverted to other vents, check and clean if necessary