I have a 90 chevy 1500 pickup
The problem i have is that you select the air mode say the defroster and the air does not blow out the defroster
It also will no blow out the vents very hard even on high
It will not blow out the floor very hard even on high

 

Does your truck have the elctronic control head or the simple HVAC dials?
Can you hear the blower kick up as you increase the fan speeds?

 

yes its electronic and i can hear the fan kick up it just seems to be going nowhere

 

Sounds like the ducting behind the dash is old. Mid 90s vechles and older used cheap thin abs plastic ducts wrapped in a sock. The problem is that over time the heat shrinks the duct, like shrink wrap for wires. It's connections warp and the air escapes behind the dash. Otherwise, the cheap foam and sound deadening fabric could have dries and is blocking the inlet to the fan blower.

If the blower is belt driven, the belt itself may have stretched or broke. Usually these fans are direct drive, where bearings in the shaft may have rusted and siezed. Try checking the fan to see if it spins freely. Behing the glove box, above the passanger's feet.

 

ok i will thanks