Voltage Regulators

To prevent damage to the battery and the rest of the electrical system that would be caused by excessive alternator voltage output, the charging system incorporates a voltage regulator to maintain alternator output within a predetermined range, typically between 13.5 and 14.5 volts. The regulator controls alternator output by sensing the battery voltage and system demand and then varying the field current to the alternator rotor accordingly.

When voltage falls below the regulator setting, such as would occur when the battery needs charging and the lights are turned on, the field current is increased, which strengthens the magnetic field and increases the charging voltage output. If the battery is fully charged and no accessories are on, and voltage exceeds the maximum setting, the regulator will decrease field current, which weakens the magnetic field and decreases voltage output.

Older vehicles used a mechanical, externally mounted voltage regulator. These used coils and contact points to regulate power to the alternator rotor, but the points eventually suffered from pitting and sticking, which could result in overcharging. Mechanical voltage regulators were replaced by electronic, solid state, voltage regulators that use transistors. Where mechanical voltage regulators generally switch on and off about 200 times per second, solid state regulators can do so approximately 7,000 times per second. Solid state regulators are available as an upgrade for many original mechanical regulator applications.

On many vehicles, external regulators were eventually supplanted by internal regulators that are integral with the alternator, which saved space and simplified wiring. Today voltage regulator function is handled by the Powertrain Control Module (PCM) on most vehicles. In addition to battery voltage and electrical demand, factors including battery temperature, ambient temperature, engine load, and other inputs are commonly used by the PCM to calculate charging system output. But if your vehicle is equipped with a traditional voltage regulator, no matter where it’s mounted, we can supply you with a quality replacement.

If you’re restoring a classic car, where appearance is just as important as functionality, we can supply you with an original equipment voltage regulator that has the right look for your engine compartment and will properly regulate voltage to protect your electrical system. If your vehicle is equipped with a solid state regulator or you want to upgrade to their superior reliability, we have the electronic regulators for all popular applications. We even offer integral voltage regulators for select applications, so you don’t have to replace the entire alternator because of a failed regulator.