It is the resistor, replace it.
Normally when a heater blower motor only works on the High setting, it is caused by a defective Blower Motor Resistor Pack. The fix is to, Replace it. In very rare instances it can also be a defective blower motor speed control switch, but rarely.
If the heater fan is not blowing on a 2001 Chevy S10 Pickup, it is possible that the fuse needs replacing. It is also possible that debris is interfering with the operation of the fan. Could also be, a faulty fan motor, a faulty fan motor speed resistor, a faulty fan motor switch,
Where is heater control switch
It has a bad "Blower Motor Resistor" The fan switch itself is fine.
Blower motor fuse is blown. Blower motor resistor burned out. Blower motor switch bad. Blower motor bad.
try replaceing the switch that controls the low to high for heater It's gonna be the blower motor resistor (near the blower motor).
Check the low speed relay and the resistor at the motor
bearing is out,replace motor.
blower motor bad or no power to it chech fuses blower switch blower motor
The blower motor speed resistor is burned out.
Bad blower motor fuse? Bad blower motor resistor pack? Bad blower motor - checck to see if it is getting power--if so bad motor Bad switch?
Your truck has both. the resistor is between the switch & blower.thje resistor controls the blower speed