Every editorial product is independently selected, though we may be compensated or receive an affiliate commission if you buy something through our links. Ratings and prices are accurate and items are in stock as of time of publication. Don't test an alternator by disconnecting the negative battery cable. Use a
voltmeter instead to conduct a simple, safe test. If you have a newer battery but your car won’t start, you may have a bad alternator. If you’re tempted to test an alternator by disconnecting the negative battery cable, don’t do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. In the pre-computer days, you could pull it off without damaging anything. Today, you risk frying every
electrical device in your vehicle. The second you disconnect the battery, the voltage regulator pegs the alternator to put out maximum power. With no battery in the circuit to act as a buffer, the alternator can put out up to 150 volts, depending on engine rpm. When the smoke clears, that “simple test” could end up costing you several thousand dollars for new electronics. Here’s a video on how to properly and safely test your alternator.Project step-by-step (2)Step 1 Conduct a Voltmeter Test
Step 2 If Your Alternator Passes
Sign Up For Our NewsletterComplete DIY projects like a pro! Sign up for our newsletter! Do It Right, Do It Yourself! Originally Published: January 04, 2019 Similar ProjectsPopular How-To Videosⓘ Can you test an alternator without taking it off?If you're tempted to test an alternator by disconnecting the negative battery cable, don't do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. In the pre-computer days, you could pull it off without damaging anything.
How do you check an alternator in a car without a multimeter?You can still check an alternator without a multimeter if you don't have any available.. Start the car and rev the engine to 2000 RPM. ... . Open the hood and listen closely to the alternator while the engine is idling. ... . Switch your car radio to the lowest frequency on the AM band, then lower the volume.. |