Assuming the lower speeds are working I would check the blower motor high speed relay in the power distribution box under the hood, if that checks out okay, check the switch.
blower resistor is bad
Blower motor NG. Blower motor resister NG. Blower motor fuse NG. Blower motor switch NG.
blower resistor
The fuse. The blower motor speed resistor. The blower motor relay. The blower motor switch. Check for power at the blower motor connection.
If you are referring to the blower motor speed control, and you only have one speed, then the blower motor resistor pack is defective and must be replaced.
The heater blower for a 2002 Chevy Silverado is mounted under the dash. It is on the passenger side, in the heater housing.
First check the fuses. If the fuses are okay I would suspect the switch and plug had a meltdown or the blower motor itself is shot. If it was the blower speed resistor that was shot you would still have high speed.
Pass side firewall.
Defective blower motor resistor pack.
I would suspect the blower motor speed resister is shot.
Sounds like the speed sensor is bad.
bad blower resistor