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How to Test a 12-Volt Generator System

by James Stevens

A 12-volt generator can be a portable unit for outdoor use to power low-voltage devices such as lighting, or may be fitted to your car to charge the battery and power the electrical equipment. Whatever type of 12-volt generator you have, it's a straightforward task to test whether it's producing the correct voltage by using a voltmeter or multimeter.

Step 1

Set your 12-volt generator running so you can test the output. If it's a portable generator, turn it on; if it's fitted to a car, then turn on the engine and open the hood.

Step 2

Locate the two positive and negative output terminals on your 12-volt generator. If it's portable, there will be two wires connected internally and a plastic connector on the end. The connector is labeled "+" and "-." If the generator is fitted to your car, look for the two terminals labeled "B" and "Gnd" on the back of the generator. Two wires extend from the generator; one is red and is attached to terminal "B," meaning positive; the other is black and is attached to terminal "Gnd," meaning negative.

Step 3

Place the metal clip on the end of the black wire from the voltmeter or multimeter onto the negative connector or terminal of the generator. Place the metal clip on the end of the red wire from the voltmeter or multimeter onto the positive connector or terminal of the generator.

Step 4

Read the voltmeter or multimeter display panel. If it reads 11 to 13 volts, your 12-volt generator is operating correctly; if it's less than 11 volts, it's not producing the correct voltage to power your devices, so you need to get it checked professionally.

Turn off the generator or car engine once you've completed the test. Close the hood of your car if you were testing a car generator.

Items you will need

  • Voltmeter or multimeter

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