What does the field terminal on an alternator do?

An alternator field disconnect is used to protect the diodes in an alternator when the battery switch is inadvertently turned to the “OFF” position. Essentially it turns off the alternator output.

What happens when you unplug alternator?

If your alternator is malfunctioning by over-charging your battery, disconnecting it may allow the alternator to provide an even higher voltage to the car electronics, and potentially damage those sensitive components.

What is the field wire on an alternator?

Find the terminal on the alternator labeled “Neg”, “F” or “Field.” This is the ground connection. Typical alternators have this terminal although some alternators don’t as they are grounded directly to the engine. The wire that connects to this terminal is black and the opposite end attaches to a metal part of the car.

Can you disconnect alternator?

If you’re tempted to test an alternator by disconnecting the negative battery cable, don’t do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. In the pre-computer days, you could pull it off without damaging anything.

What should alternator field voltage be?

A good alternator should maintain battery voltage between 13.9 and 14.8 volts (14.2 is optimum).

Will car stay running if battery disconnected?

If the engine’s already running, disconnecting the battery will still keep the engine running. If you’re trying to start a car without a battery or with a very dead battery, it won’t start (even with push start in a manual car) because there’s no electrical supply (spark) to the combustion chamber.

What are the 3 wires for on a alternator?

The three wire types in a three-wire alternator include the battery positive wire, the voltage sensing wire, and the ignition input wire. The battery positive wire connects to the starter. The voltage sensing wire connects to the battery, and the ignition wire connects from the alternator to the key switch.

Does an alternator need a fuse?

The primary alternator fuse (or fusible link) will blow whenever there’s excessive current flow due to a short circuit or other malfunction. Most of the time, there’s a high-amperage fuse or fusible link between the alternator’s battery terminal and the battery.

Why excitation is required for alternator?

The excitation system is responsible for supplying the field current to the main rotor. The requirements of an excitation system include reliability under all conditions of service, a simplicity of control, ease of maintenance, stability and fast transient response.