Other than a defective motor, a bad switch or blower motor resistor assembly can cause an inoperative heater blower motor.
Problems for specific Mercedes-Benz 400SE years:
Car problem reports
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Most reported Mercedes-Benz 400SE problems
The climate control system can fail or perform erratically due to internal problems with the climate control button electrical contacts. Replacement of the climate control assembly is commonly required to correct this problem.
The head lamp wipers are easily damaged, especially by automatic car washes.
A refrigerant leak may develop from one or more of the following AC components: AC compressor, hose manifold for the compressor, or the evaporator core. The loss of refrigerant can cause poor AC performance. Our technicians tell us that proper leak diagnoses should be performed in order to determine the cause of any refrigerant loss.
Ports in the cylinder head related to the emissions air injection and EGR systems can clog; the cylinder head should be removed and the ports cleaned.
Due to wear, high usage vehicles can experience ignition lock and tumbler failures. The ignition lock cylinder will generally require replacement to correct this concern.
Problems with the pneumatic system can cause closing assist and door lock issues.
One or more door windows may stop working due to a failed window regulator. Replacement of the failed regulator will be necessary to correct this concern.
The lenses for head lights may become opaque (cloudy or hazy) as a result of sun exposure. This can reduce the effectiveness of the lights. Our technicians tell us plastic polishes can improve the clarity of the lenses, but replacement of the lamp housings is necessary to regain full intensity of the lights.
The lower control arm bushings can wear and crack, leading to irregular and premature tire wear. Worn Ball joints can also cause similar tire wear problems. I some cases it may be necessary to replace the lower control arm, including bushings & ball joint to correct this concern.
Vehicles with automatic level control that ride harshly in the rear (no give in the suspension) may have one or both dampening actuators which have failed. It is commonly recommended the actuators be replaced in pairs.
A cracked or broken heater core outlet housing can cause a coolant leak near the bulkhead (firewall). Our technicians remind us that coolant leaks should be repaired in order to avoid overheating the engine due to coolant loss.