You most like have a bad blower motor resister.......
Defective heater resistor pack.
Check your coolant. Is it thick and gunky?
Maybe because your climate control system needs to be repaired....
the heater fan resister,it is or should be on inside or on outside heater box.
The blower motor speed resistor is burned out.
try replacing the blower motor resistor
The first thing that you need to check will be the coolant level..................
Most likely and bad blower motor resistor.
Defective Heater Resistor Pack.
Check the low speed relay and the resistor at the motor
try replaceing the switch that controls the low to high for heater It's gonna be the blower motor resistor (near the blower motor).
try the bend door