How To Test Alternator Voltage. This time connect your meters red lead to the B terminal on the back of the alternator. Many times an alternator is not working correctly because of poor electrical connections in the charging circuit.
Then start the engine and check for increased voltage readings. Connect the voltmeter probes on their respective battery terminals. If voltage seems to fluctuate during your test switch your voltmeter to the AC voltage scale and take another output voltage reading with the engine still running.
Unlike changing the windshield wiper blades or changing a headlamp light bulb this is one check-up that drivers are reluctant to doThey rather go visit a garage or dealer.
If its below that charge the battery with a battery charger before you conduct the test again. To check for a bad alternator diode you may want to reset your voltmeter to the lowest possible AC voltage scale setting. For the easiest method to check your alternator simply turn on the headlights to your lawn mower or outdoor power equipment. Then turn off the engine.
