Mercedes-Benz W140 heater blower not working
W140 heater blower does not run even though the fuses are good - what is the fault?
A common cause is the blower motor wire connector, which has overheated and loosened. Check the connector first and make sure it sits tightly. Other causes are a broken motor or switch.
W140 blower does not work on some speeds - what is checked?
If only some speeds are missing, the fault can be in the center console switch or in a burnt connector or pass-through. Also keep the blower bearings in mind: they can seize if the resistor has failed.
How do I know if the blower motor is broken?
Measure at the regulator control terminal whether power is reaching the blower. If power arrives but the blower does not run, the motor is probably broken. The motor is located under the fresh air filter.
W140 blower runs even though the power is off - what is the cause?
The speed regulator is in the blower's aluminum housing, and water can get into it, for example when the engine bay is pressure washed. Moisture can start the blower. Have a workshop investigate the electrical fault.