Alternator Wiring Diagram

This topic deals with the trouble shooting and repair of  the alternator in our cars. The Alternator it self  in this example is just 40 Amp/ 12 volts. The rectifier and the regulator is internal. But first we have to know some basic things about the alternator. Why do we need it in our cars ? Basically it is just the charger of our battery, so that the power lost by the battery will be replenish again for some other used like for starting the engine time and time again and some other load like, glow plugs, lights, horn, and many more. If we open an alternator we will noticed that it is just composed of three things :

1. Generator – This generate the alternating current

2. Rectifier – Converts the a/c power to d/c

3. Regulator – This regulates the output power so that we could not over charge the battery and the parameters for voltage and current is in range for consumption to avoid damage for the device and the loads, since the acceleration of the engine is always changing. This is accomplished by varying the supply of the field coil by the use of slip rings in the shafting.

Wiring Connection

Wiring Connection

How to test the Alternator:

1. Connect the wiring in the figure. In this sample, I got  a  5 w/ 12 volts bulb. If you followed the wiring correctly the light should be on like in the picture.

2. Measure the voltage in the battery terminal. In this case it is 12.5 volts

Alternator with drill machine

Alternator with drill machine

3. Connect a drill machine with socket wrench and run the drill. You will noticed that the light bulb will slowly turn off as we increase the speed of the rotation of the drill machine. You should have a volt meter or a tester to measure the terminal voltage. When the bulb completely turn off measure again the voltage, It should register a reading of  14 volts to 14.5 volts . Depending on the alternator and the battery charged level. If that is the case we could say that the alternator is charging the battery. If we have a clamp meter ( d/c clamp meter ) we could find out how much current does it is charging the battery.

4. Some problems that we may encounter in our alternator is the carbon brush if it is worn out already. So you might want to check it first before deciding to replace anything.

Regulator assy

5. Here is another sample of a Regulator/Rectifier assembly.

Regulator / Rectifier

6. If your problem is how to remove the pulley and the cooling fan so  you  to transfer  it to the new unit that you bought. You have to dismantle the alternator, and put the body of the rotor on a vice and remove the nut that holds the pulley in placed. Then you can now  remove the pulley and the cooling fan.


Here is  a sample of a stator of the alternator







This entry was posted on Monday, January 4th, 2010 at 2:57 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

4 Responses to “Alternator Wiring Diagram”

  1. moubeen Khan

    you peopel r doing a very good job and thanks for the help

  2. cezar ramos

    thank sir for how to make a trouble shot the alternator for a wiring diagram…

  3. edison delos santos

    my car problem are the the battery become weak, when i leave my car in 1 week and then i need to start it , it doesnt work anymore so i need to charge the battery.what is this problem? thank u so much!

  4. Jeff

    Does the alternator give a charging if the two small wire not connect to their source? I mean, just connect the 10′ Battery pole to Battery +ve?

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