How to test alternators?

How to test alternators?

Before checking each alternator element individually, you must perform a cleaning, removing grease, dust, and mud without using solvents by simply rubbing it with a cloth. During disassembly, it will be checked that there are no breaks, deformations, or excessive wear. In this article, we read about How to test alternators?

To take into account before mounting and dismounting the alternator on the vehicle.

  • When mounting the alternator in the vehicle, consider its polarity before connecting it since if you reverse the contradiction in the battery, the diodes can be damaged.
  • The alternator must never run without load, that is, with an open circuit.
  • Before removing the alternator from the vehicle, for checking or repairing it, disconnect the battery.
  • If you are going to perform electric welding operations on the vehicle, first disconnect the alternator.

Now, test the alternator with a voltmeter. If you see that it is within range, it is good. Connect the meter leads to the battery terminals and look for 13.8 to 15.3 volts (from the engine running, lights, and rest accessories). This means that the alternator is pumping out the juice.

Don’t do it if you’re tempted to test an alternator by disconnecting the negative battery cable. A well-made alternator can keep the engine running, but it was never a good test because today, you would risk frying all the electrical devices in your vehicle.

The second the battery is disconnected, the alternator voltage regulator pins to turn off full power. The alternator can shut down up to 150 volts with no battery in the circuit, depending on the engine revs. When the smoke clears, that “simple test” could end up costing several thousand dollars for new electronics. Instead, you can get a cheap voltmeter and with the engine of the battery voltage. It should be between 12.5 and 12.8 volts. If it is below that, you need to charge the battery with a charger before testing.

Alternator large to test alternators

Now, start the engine and check the increase in voltage readings as shown above. Suppose you see higher readings, the alternator most likely good (more sophisticated testing equipment needs to detect an open or shorted alternator diode). A dead battery in the morning usually caused by a computer module not shutting down when the car turns off. 

Bottomline to test alternators

We hope you have successfully tested the alternator. Suppose you want to learn the entire automotive electrical system. We invite you to participate in our following courses on Electricity for Automotive Electronic Diagnosis. Follow us on Facebook, comment, share and live the Autosoporte experience.

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