heat only blowing out of the vent. 2003 chevy 2500 hd

[72 Bogger]

The blower only blows out the vents. Ive replaced the contols in the dash with no luck
Iany body have this problem and fix it?
I tryed to google it and didnt get a clear answer.
So I figured id post it on here and see what you guys said
Any help would be appreciated. 

[95-Jeep]

Have you recently changed the battery?  If so un hook wait a few and hook it back up.

or hold the auto button on the heater for a few seconds that reprograms the actuator

if those don't work its more then likely the actuator or blend door

[burl]

Or a rod fell off the mixer door... had it happen on my 03 blazer