In a 2004 Volvo S60, if the blower motor only operates at one speed, it is likely due to a faulty blower motor resistor or a problem with the blower motor itself. The resistor controls the different speeds of the blower, and if it fails, the blower may default to a single speed, usually the highest. Additionally, issues with the vehicle's HVAC control module could also contribute to this problem. A thorough inspection of these components is recommended to diagnose and resolve the issue.
Probably your blower motor speed resister is burned out.
There is a resistor near the blower that is bad, known cause is high speed only.
The blower motor resistor pack is bad.
The blower motor speed resistor is burned out.
Blower speed resister is burned out.
The blower motor fuse protects the blower motor electrical circuit. The blower motor relay operates only the high speed function of the blower motor. The blower motor speed resistor operates the lower speed functions of the blower motor.
Blower motor speed resistor is partially burned out.
If you look in the manual you will find that position 1-3 and position 4 BOTH have a fuse. Try replacing the fuse for position 4...
either the blower control switch or the blower motoer needs replacing
Bad blower resistor?
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.
The blower resistor has failed. It is located at the very bottom of the passenger side of the dash.