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How To Test A Car's Alternator

How To Test A Car's Alternator

The battery symbol lighting up on the dashboard is the clue that your car's alternator need to be tested. This indicates a problem with the charging system which has terminals and connectors to the alternator which also affects the battery if it does not work. Before you check underneath your car, these tips might be of help.

Right, we're now going to try and show you some simple tests to do to show you if the alternator's working once the light on the dashboard comes on. The light on the dashboard would be the battery symbol which will show you there's a problem with the charging system. The first thing we would need to do is look at the battery connections to make sure that they're tight first, like so, as soon as you're making contact.

The next thing to do would be to do a voltage check on the battery which you would do providing that you've got the multimeter like so and basically by testing the voltage on the battery, it should read more than 12 volts. This is a 12-volt battery. This one, as you see its reading, is 12.

34 volts which shows the battery is fine. The next test we would do is we would look at the alternator underneath the vehicle to make sure that the connections are all intact. There's not a broken wire, there's not a terminal mixing up with the alternator, and it's not excessively corroded.

I'll now show you how to do that. You can see here, the terminals, connectors, are on the back of the alternator which is checked to make sure they're both intact. They're not excessively corroded and they're both there, basically, which shows that yes, they are both there and they're both connected.

That's okay. The alternator belt or auxiliary belt is intact, so that's fine. Make sure the back is also intact.

Right, one of the other main things to check is there will be some brakes or fuses that will be connected to the alternator system. It's just to do a visual inspection to ensure that none of those are actually blown and know they're all intact. So, that shows that part of the system is intact.

The other way to test would be to actually start the vehicle and then test it with the multimeter. With the vehicle not started, we get a reading of 12.34 volts which is what's actually in the battery.

If the alternator system's working, that should then increase to a minimum of 14 volts while the engine is running. Right, now with the engine running, we need to check the voltage that's now pumping out. As you can see, the alternator is now producing 14.

05 volts which shows that the alternator's working fine. If the alternator's not working fine, your reading will not increase by any amount. It will still show the amount shown in the battery.

And with the alternator not working, the battery will just become flatter and flatter and flatter. If in doubt or you haven't got it tested, consult your local garage. They'll point you the direction. .