12 With the cover off, you can see how a mechanical voltage regulator functions. On the left is the field relay, which closes when the ignition is turned on. On the right is the voltage limiter, which is the actual voltage regulator. The field relay is a simple on/off switch. Turn the ignition on and you hear a “dink,” which is the field relay contacts closing. The voltage limiter has two contacts and works between the two to energize field windings and charge the battery. Rapid on/off contact exists back and forth between the two contacts to help maintain a constant 13-14 volts.