The starter is the single largest power user and most critical to your car’s operation. The starter is simply a DC motor that turns the engine through the flywheel. Voltage to the starter is supplied directly from the battery and is controlled by a relay and/or solenoid operated from the key switch inside your car.
Starters can be of varying types and designs – gear-reduction types for higher torque, permanent-magnet types to reduce size and old-fashioned heavy starters. But whatever the type, they all function in the same basic way.
A slow cranking engine could be a sign of an old or bad starter. But most likely, it’s due to low battery voltage, poor electrical connections at the battery, or a failed relay or fusible link.
Starting a car with the major components turned off (like the AC compressor, blower motor and high-powered stereos) will greatly ease the load on the starter. In fact, most new cars have “lock out” relays that will not allow the AC compressor and alternator to turn on until after the vehicle has been started. But turning these power-hogs off before shutting off your car is always a good precaution.
Although the starter drive, or “Bendix” as it was commonly referred to, can be replaced separately from the starter assembly, it’s rarely recommended anymore. Failure of any part is due to age, usage, and/or heat stress; factors to which the entire starter has also been subjected. That is to say, all the other parts of the starter system are just as old and stressed. Replace the starter as a unit and have the electrical system checked at the same time to prevent further problems.