How To Test If I Have A Bad Alternator. Turn on your engine and test the voltage again. Usually, a bad alternator diode will cause your headlights or instrument panel lights to flicker or dim and, sometimes, drain battery power overnight, or in minutes.
Power the engine at least 2,000 rpms for testing purposes. Observe if the car engine is running like earlier. Easy way to test your alternator in less than 3 minutes with simple tools found in most garages.
A very simple way to test if your alternator is bad is to first start your car. If this happens the alternator is doing good. A multimeter measures voltage as well as other electrical properties such as current and resistance.
If your car keeps running upon unplugging the battery, it means the alternator is in good condition. How to test an alternator. If the voltage is lower than 12 volts, the issue might be with your battery.
Once connected to a terminal, an alternator should test between 12 and 13.5 volts. Connect the voltmeter probes on their respective battery terminals. There are two tools that can be used to test an alternator.
To check for a bad alternator diode, you may want to reset your voltmeter to the lowest possible ac voltage scale setting. If any of these becomes faulty, your alternator will not be able to work efficiently again which will lead to it failing and you being at risk of a major inconvenience. Have your assistant start the car’s engine and let it run for a few minutes at 1200 rpm.
You should read “0.00” in the display. Observe if the car engine is running like earlier. However, a very simple way to check if the alternator is working is to run the car and disconnect the positive terminal of the battery.