How do you test a car alternator do see if it is working properply with battery cables?

Okay, this mechanic told me a long time ago, but I kind of forgot. But he said that you could connect battery cables to both cars. He said that if you removed the negative (I am not sure) from one of the cars. It would give you a indication if the alternator was good. If the car in question alternator kind running after you removed the negative lead. It is good, but if it dies out, then the alternator is no good. But I just need some clarity. Any help would be appreciated. Thank you.
How do you test a car alternator do see if it is working properply with battery cables?
At best, that method seems a little %26quot;hit or miss%26quot;, no matter what the age of the car. Even with a bad alternator, the jumped car might or might not stop running when the jumper cable is removed, depending on how low the battery is.



The simplest way to see if your alternator is working is to use a multimeter ($30 or less) to test the voltage across the battery terminals. It should be about 14.5 volts with the engine running, and a little over 12 with it off. If it's the same with the engine on or off, the charging system isn't working. It might be bad connections, but it's almost always the alternator.
How do you test a car alternator do see if it is working properply with battery cables?
That was a trick used on old pre computerized automobiles. Removing the pos battery cable while car was running and if car stayed running alternator was fine. HOWEVER..... Modern electronically controlled vehicles should never be tested like this. You run the risk of damaging certain electronic devices by performing this test.
How old of a car are you talking about? 50's or 60's? Don't do it on a car made after 1981 or so or you may cause damage. Just take it to the parts store and get it tested for free.
Once you jump start the car and it is running, disconnect the jumper cables. if it stays running after removing jumper cables then remove positive cable from battery. If it dies at any time , most likely it is your alternator.

Like the others said Dont do it on a newer car!
you don,t want to do that on theses new cars today.
if your alternator wasn't working your battery light would be on in the dash.
check the voltage on the battery before you start the car with a dc volt tester(should be between 11-12 volts) start the car and check the battery voltage again with rpms at about 2000 battery should show 13-15 volts if it charging.As others have said removing cables while running can damage some vehicles