The voltage regulator controls the amount
of voltage being output by the vehicle’s alternator, based on the car or
truck’s demand on the electrical system. The voltage regulator ensures that all
your of your automobile’s electrical components are running correctly and that
the battery is neither overcharging nor undercharging. To do this, it keeps the
voltage in the system between about 13.5 and 14.5 volts, as this is sufficient
to recharge the vehicle’s battery safely without affecting the electrical
circuits and components of the car or truck. When the alternator output gets
too high, the regulator stops the flow of electricity from the alternator to
the battery to prevent overcharging; when it gets too low, it allows the
electricity to flow to the battery again.
Often this is achieved through an
electromechanical process. The voltage from the system supplies power to a coil
of wire in the regulator. This creates an electromagnetic field that pulls a
magnet attached to a switch. Higher voltage pulls the magnet, which pulls the
switch to the off position. In lower voltage situations a spring attached to
the switch is able to overcome the weaker pull of the magnet and pulls the
switch into the on position. In some vehicles a similar effect occurs through
more complicated electronic controls. Some vehicles forgo the use of a
dedicated voltage regulator and instead regulate the alternator’s output with
the vehicle’s computer.
Prior to the late 1960s – early 1970s, most cars and trucks had a voltage regulator that was separate from the alternator; this type of regulator can be found mounted on to the outside of the alternator or to the firewall or inner fender. While a few models today still do have a separate voltage regulator, the majority of vehicles nowadays have the regulator built internally into the alternator.
