heat flow to floor stopped on 2000 Chevrolet S10

Defrost and Dash heat but wont come out at feet

Asked by for the 2000 Chevrolet S10
Pickup or Blazer? IF P/U, which engine, 4 or6 cyl?
2000 s-10 pickup with a 2.2 litre engine
"NO" air from floor at all with the truck parked and engine at IDLE? While driving does it ever switch from vents to deffrost on it's own?
Wher is the air mode activater?