Pull Battery Cable To Test Alternator

Start vehicle and voltage on voltmeter should increase to around 13 volts and stabilize there.

Pull battery cable to test alternator.

A good alternator may indeed keep the engine running without the negative cable but this was never a good test. What are your thoughts. But it s no longer a safe test to perform on a modern vehicle. 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. Can you test an alternator by removing battery cable. Testing alternator by removing battery cable was a valid test back in the day before computers. Use a volt meter to test the voltage.

Doing this would allow you to check whether the alternator is putting out enough current to run the vehicle. If the engine cuts off it is a sure sign that the alternator has died. If you re tempted to test an alternator by disconnecting the negative battery cable don t do it. 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. Some newer cars will turn off even if the alternator is working good. Community answer test alternator by connecting voltmeter on dc 20 red on positive battery terminal and black on negative battery terminal.