Can you hear the blend door moving inside the HVAC housing when you operate the selector dial on the dash-the one that selects heat, vent, defrost, etc? The blend door on a 97 is mechanically actuated. If the door is not moving it may be broken inside the HVAC housing or there may be a broken linkage or cable on the HVAC housing. You need to get under the dash and take a look. Maybe remove the glove box so you can see better.

Dodgeramguy is right, usually when the heater core is bad you will smell coolant in the cab of the truck and sometimes get a sweet-smelling exhaust/fog coming in thru the vents on the dash.

If the blend door and the cables/linkage are OK, you may need a new thermostat to fix the problem.

 

ok great! I'll take a look at some of these things, and I'll just get a thermostat since they are cheap, won't hurt.