I tried and switch from the face/foot vents to defrost the other day and when i tried to put it back to face/feet it didn't change. only air coming out of defrost vents now. Temp will change from cold to hot. Need help to start to look at what could be causing the problem.

 

Probably have some blockage in the vents from leaves and other debris (happens often). Get a vacuum to clean that out.
I would also check your coolant and see if that system needs to be flushed.

 

Most likely your mode actuator has given out, try the relearn hgt posted and see if anything changes. If you find someone with a tech 2 there may be a actuator stuck code or circuit code in the hvac module. Leaves will only cause issues with airflow (stopped up cores) and temp door, they cant get past the heater or evap core to the mode actuator door due to how hvac cases are designed.

edit: btw there is two hvac fuses, you need to pull the one labeled hvac/pk3+, its fuse #10 on the bcm diagram label. no need to pull #16 (hvac/ip ign) because that is your key on signal.