I hope you checked the fuse.
The heater blower resister is under the dash on the passenger side. It is inserted into the side of the blower motor case.
The year, make and model info would help but generally the heater blower motor resister is located close by the heater blower motor.
I found the resister, it is a small module held by 2 small screws on the base of the heater blower behind the glove box.
The most likely problem with the heater blower on your 2003 Sable is the blower resister. The resister can go bad and cause you to only have one speed.
You most likely will have a bad blower resister........
It is under passenger side dash behind the blower motor.You must remove blower motor to access it.
resister is located on the plenum next to the blower motor under the hood
should be the connector in the ac housing closest to the blower motor
how do you change heater blower resister merc a class
No. The ac and heater fan only has one resistor. The control switch is also failure prone on that vehicle.
Check the blower resister
Replace the resister, if that doesn't work replace the blower motor.