how can i test my alternator to see if it works ok?

Answer 1

No don't disconnect the battery cable on a newer car---not a good idea, but that works for very old cars....

Buy a voltmeter, set it to something above 12V (like 20) and put one lead on the POS and one lead on the NEG. Have someone rev up the engine.

Here's some good advice on how to do it:

http://autorepair.about.com/cs/electrical/a/aa122700a_2.htm

Answer 2

The simplest way without taking it to a garage or buying something you may never use again is wait until its dark,then start the car, put all the lights on and anything else you can think of (heater fan,rear demister, etc). Place the car in-front of an object (another car or wall). Now let it tick over and then rev the engine up to about 2000rpm,while doing this have a look at the front to see if the lights are getting brighter.If they are its working,this doesn't tell you how well its working tho.
If your not satisfied then get a volt meter and test it,it should read about 13.6-14v when the engine is running.
If your car has a ECU don't disconnect any of the battery leads as it will damage it,disconnecting one of the leads is only OK for older cars.

Answer 3

Never ever disconnect the battery while the vehicle is running especially on a computer controlled car. The resulting voltage spike will fry sensitive electronic components. If you have a voltmeter you can place the leads across the battery and check the voltage being produced by the alternator. If you have anywhere from 12.8 to 14.2 volts is acceptable. You won't however be able to check the amperage that the alternator is capable of producing without the use of a specialized ammeter. If the car won't take a jump, then the battery is probably junk. Most times if the alternator lamp on your dash goes out after you've started the car then you can be somewhat assured of the alternator integrity.

Answer 4

Start the engine & turn on your headlights (to provide a load). Attach a voltmeter to the battery terminals and rev the engine. The voltage should be about 13.5 volts, and should rise & fall as you rev and slow the engine. If so, then the alternator is putting out the proper volts. The higher, the better, as long as the reading doesn’t exceed 14.75 volts. That can overcharge your battery.

Do NOT disconnect the battery with the engine running! A] you'll fry the electrics and B] the battery needs to be in circuit for the alternator to work at all.

Answer 5

If you have to ask you could do some/a lot of damage if you get it wrong. A basic user test is to switch the main beams on, then start the car. If the lights dim as it cranks then get brighter the alternator is doing its job. If they stay dim then its suspect. Generally if the battery keeps enough charge to run the car then the alternator is more or less ok

Answer 6

You will find that most motorest shops that sell batteries will test it for free , failing that buy a cheap , electric test metter put on 200 volts clip red lead to positive side of battery and black to negertive with the engine running at about 2500 revs it should rise to about 14 to 15 volts

Answer 7

Spend $15 on a cheap voltmeter and measure the battery while the engine is running. It will be about 14 volts if the alternator is good and 12.5 volts or less if it's bad.

Answer 8

Take the car to your local garage, they will test it in the car, probably won`t even charge you, 2 minute job... but they will charge you for a new alternator and to fit it if it is faulty

Answer 9

Here's a great article on how to test an alternator and avoid frying your car's computers.

http://free-auto-repair-advice.blogspot.com/2007/09/avoid-bogus-alternator-test.html

Answer 10

Take it to Auto Zone, they have tester on the floor. If you can drive the car, they have a machine to test it on the car running.