Each starting of the car demands a lot of electricity. Besides that, a lot of other systems in the car demand a constant supply of electric power. An ordinary battery would dry out very fast, so the car uses a rechargeable battery to power up everything. The battery is recharged by a very important car component – an alternator.
But how can you wire an alternator to charge the battery constantly? Most alternators have four wires. The black, negative wire has a grounding role and is connected to the chassis. The first red wire is a main positive that connects the alternator and the battery output port in the back. The sense wire connects to the side of the battery to the voltage regulator. The last is the field ignition input wire connecting to the ignition warning lights.
Knowing this will shed some light on the subject, but there is a lot more that we should cover. What is the alternator, and how does it work? How many wires can go to the alternator? How to identify the wires? These are only some of the topics that we will explain. Stay with us!
What is an Alternator
When talking about the importance of engine parts, it is hard to pick some of them out. But, the alternator is one of the most essential parts of the engine. It handles producing electricity by converting mechanical energy into electricity.
An alternator sends the electricity to the battery for usage and storage. At the same time, it can recharge all the used electricity during the drive.
How Does an Alternator Work
The internal components of the alternator are connected with a belt. When you turn the ignition switch, the belt starts its rotation and creates a magnetic field. The magnetic field goes through a series of coils called windings. Electricity is made in those coils.
The alternator is connected to the battery, and from windings, the electricity is sent to the battery. There it can be stored and used when needed. This way, the battery can always be recharged during the drive.
Check Out How Alternators Work – Automotive Electricity Generator:
Alternator Wiring Harness Overview
Gauge
Alternator wiring demands a certain wire size. Connections can become too loose if the wiring is too thin. That is why using 10, 12, or 14-wire gauges is recommended.
Colors
The red color is the most common color used for high-voltage wires. The positive wire is always connected to the positive terminal on the battery. Sometimes it can be a green or a blue color wire to mark an especially high voltage wire. The grounding wire is always black.
Terminals
Two types of terminals are attributed to the wire harness of an alternator. There is a ring and a spade terminal. A spade terminal connects the wire and the alternator. The ring terminal connects the wire to the battery.
How Many Wires Go to an Alternator
It all depends on the type of alternator. In most cases, three or four wires go into the alternator. In the case of four, those are the main positive wire that supplies the electricity and the main negative wire that serves as a ground wire.
There are two more wires. The first one is the sense wire that notifies the alternator about the current use of power in the car. The final wire delivers power to the field coil, where the magnetic field is created.
Alternator Wiring Diagrams
Above, we described the case where the alternator has four wires, which is the most common case. Below we will cover all of those wiring patterns in more detail, so you can know the difference.
4 Wire Alternator Wiring Diagram
If the alternator has four wires, we will explain its purpose and how to connect them. The first wire is always the ground wire, usually black. The second wire is red, carrying the power from the alternator to the battery.
The third wire is a sensing wire. Its purpose is to notify the alternator about the current needs of the rest of the electrical systems in the car. The fourth wire handles deliver power to the field coil (windings). From there, the coil creates the magnetic field. That field is used for producing electricity.
3 Wire Alternator Wiring Diagram
As the name says, there are three connections in the three-wire alternator. The first large connector connects a battery and an alternator. The other two connectors are smaller spade connectors. They are located on the top of the alternator.
One of those two is a sense wire terminal. The sense terminal is connected to the output of the alternator. That way, the terminal can sense and manage the battery voltage output. The other terminal is the exciter. The exciter delivers electricity to the windings of the alternator.
2 Wire Alternator Wiring Diagram
This type of alternator has three connections. Out of those three, the first one is the ground or an output connection. It is connected to the car chassis. That allows power to flow through the alternator to other car components.
A second connection is a positive wire, usually colored red. It is connected to the battery and delivers power to the alternator. The third connection is also grounded.
1 Wire Alternator Wiring Diagram
There is no ground wire or connection to the harness when you have one wiring alternator. The only wire you will see is the red wire connecting the alternator and the battery.
There are some minuses to this alternator option. One wire alternator doesn’t have a battery light which is a warning for the battery and its condition.
FAQs
What sends the signal to the alternator?
An engine control unit (ECU) notifies the alternator that it needs a certain amount of power to run the vehicle. The alternator is responsible for transferring the exact amount of power needed. It has components employed to deliver the demanded amount of electric current.
How Many Amps Does an Alternator Charge a Battery At?
When using an alternator with 40 amps, it takes around half an hour to charge a battery completely. But in the end, it all depends on the battery and the vehicle. Larger vehicles have alternators that have between 100 and 200 amps. It is recommended to use those alternators to charge those batteries.
Do you connect red or black first?
First, the red positive wire connects the alternator to the battery. Next comes the black negative wire.
How Do I Know If My Alternator Is Not Charging My Battery?
Several signs can point out to a faulty alternator:
– Headlights dimming or glowing more brightly than usual
– Electric systems working poorly or slowly
– Problems when starting a car
– Frequent stalling when driving
– Strange noises coming from under the hood
– Battery indicator flashing on the dashboard
Problems with an alternator can start from different reasons, and the most common are:
– Worn carbon brushes
– A problem with a fuse
– Issues with wiring or connectors
– Broken serpentine belt (it powers the alternator)
Does the Alternator Charge the Battery When the Car Is Off?
The engine needs to be running so the alternator can charge the battery. Alternators can charge the battery when idling or driving. But in every case, the engine needs to be running.
Final Considerations
Wiring an alternator is an underrated skill. It may never need you, but it can be a true lifesaver once it does. There are different types of alternators, but once you get the hang of it, you will have no mysteries.
An alternator is a part that doesn’t have regular maintenance but can still be damaged. Knowing how to diagnose the problem and how to solve it is a skill that keeps you with a complete and running car battery.
For more practical advice, keep an eye on our blog!
