You will most likely have a bad blower resister..............
Resistor pack on blower motor? Fan switch? Low speed relay?
Could be, a blown fuse, a bad blower motor, a burned out blower motor speed resistor, a bad blower motor switch,
A typical blower motor relay only operates the high speed function.
Low speed relay bad Blower fan resistor Defective winding in blower motor
Blower motor speed resistor is partially burned out.
Could be, blown fuse, bad blower motor, bad blower motor speed resistor, bad blower motor switch,
99% of the time, the blower motor relay, or resistor block,will be bad if the fan motor only works on high speed.
The blower motor resistor pack is bad.
The blower motor speed resistor is burned out. You can replace only the resistor but the resistor probably burned out because the blower motor is going bad. If you want to fix it for good, replace both the blower motor and blower motor speed resistor.
Replace fan switch.
replace the blower motor resistor
blower resistor is bad