Glossary of Terms - Starter & Alternator

Add-on Regulator
Some alternators use an add-on type regulator that is mounted on the outside of the alternator housing.

Alternator
A belt driven device that creates electrical current for maintaining the charge state of the battery and the electrical requirements for the vehicle

Ampere
Commonly referred to as amps, this is an electrical unit of measure. Alternators are rated by the amp output capacity at a given voltage.

Battery
An electrical storage device used to supply electrical current for starting a vehicle.

Charge Lamp
A light in the vehicle instrument cluster that illuminates when the alternator is not charging or when there is a fault in the charging circuit.

Core
This is the old unit being removed from the vehicle.

Diode
Diodes are used in pairs (positive and negative) to change the alternator output from alternating current (AC) to direct current (DC).

Direct Drive Starter
This type of starter has the drive gear attached to the armature or utilizes the armature as the drive gear.

External Fan (EF)
This alternator design has a fan mounted on the outside of the alternator that directs air flow across the internal components for cooling.

External Regulator (ER)
Some alternators use a voltage regulator that is not attached to the alternator. It is usually found on the fender well.

Flywheel
This is a large gear mounted to the back of the crankshaft which turns the engine when the starter is cranking.

Internal Fan (IF)
This alternator design has two fans built together with the rotor inside the alternator that directs air flow across the internal components for cooling.

Internal Regulator (IR)
Some alternators use a built-in type regulator that is mounted on the inside of the alternator housing.

Offset Gear Reduction Starter (OSGR)
This type of starter uses an internal gear set used to increase torque. The internal gear sets are offset which means the drive gear and motor rotate on different axes.

Permanent Magnet Starter
This type of starter uses magnets for magnetic poles rather than coils of wire (field coils). These units are lighter in weight and smaller in size.

Planetary Gear Reduction Starter (PGR)
This type of starter is similar to the Offset Gear Reduction, however the gear sets are not offset which means the drive gear and motor rotate on the same axis.

Rectifier
This is an electrical component in the alternator that contains sets of diodes which are used to change the alternator output from alternating current (AC) to direct current (DC).

Solenoid
This is an electrical switch on the starter that once energized allows the starter to engage the drive gear into the flywheel during starting.

Starter
This is an electrical motor that cranks the engine by moving a drive gear into the flywheel, thereby rotating the crankshaft.

Starter Drive
This is the gear on the starter that engages the flywheel, causing the engine to crank.

Voltage Regulator
This is an electrical component used to maintain the proper charge state of the battery by regulating alternator output.