Mercedes-Benz W639 heater blower faults
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W639: the blower works only at the highest speed, what is the fault?
The blower speeds are controlled by the resistor pack, which is under the storage compartment in the middle of the dashboard. If the low speeds do not work, check the resistor, the switch positions and the blower control voltage. A sluggishly turning blower can also blow the resistor's fuse.
W639: the blower fades and stops within a few seconds, what is the fault?
The cause may be worn-out brushes in the blower motor. The brushes wear out at around 200,000 km. The motor can be reached by removing the centre compartment and the plastic grille.
W639: the air does not flow properly and the blower makes a hissing sound, what is the fault?
A dirty and damp fresh-air filter can block the airflow when recirculation is off. Fitting a new filter removed the symptom. The filter is worth replacing first, because it is easy to check.
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