Pull Battery Cable To Test Alternator

Testing alternator by removing battery cable was a valid test back in the day before computers.

Pull battery cable to test alternator. Start vehicle and voltage on voltmeter should increase to around 13 volts and stabilize there. Connect it to the battery and it should read a little above 12 volts when its off and 13. Some newer cars will turn off even if the alternator is working good. What are your thoughts.

Pcm tcm electronic power steering radio etc. To do a quick check on an alternator i was told that you could start the car and then remove the negative battery cable. Use a volt meter to test the voltage. If the engine cuts off it is a sure sign that the alternator has died.

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. If it decreases and starts to drop until vehicle eventually dies you have a defective alternator. Technically yes but that test can also wind up destroying all the electronics in your car.

Today you risk frying every electrical device in your vehicle. Community answer test alternator by connecting voltmeter on dc 20 red on positive battery terminal and black on negative battery terminal. But it s no longer a safe test to perform on a modern vehicle.