Use a vom meter, or battery tester and with the engine running voltage should be approximately 14.5 volts.
The alternator is here to give power to / recharge the battery while the engine is running. the alternator, when wired correctly isn't charging with the engine running, then you can tell it is not working anymore. how to know : ideally you'll need a volt meter to controle voltage on the battery +/- plug while engine is doing ~1200rev. bit more elaborated : follow the + cable from the battery to the alternator connection, then with the engine running mesure voltage between the alternator connection and any negative ( - ) spot that you are 100% sure of (i.e. the head of a bolt screw onto the car) a good alternator will give you a reading around 14 for a 12V system (most popular) What happen when the alternator is not working properly : Your battery keeps on diying.
Have a shop load test the battery.
I can tell you that on a 2000 mercury cougar it is a fuse on the positive cable between the battery and the alternator
A quick way to tell if there might be a problem with an alternator is to remove the positive side battery cable from the battery while the vehicle is idling. If the engine dies, odds are there is an alternator problem.
Take the battery to a parts store so they can test it.... Actually you need to test both the battery and the alternator because if your alternator is not functioning correctly it can drain the battery of power... so just testing the battery may only tell you that you have a drained battery and not reveal the cause... This testing can be done using an Auto meter which tests the battery and also does an alternator load test...If you do not have a tester you can rent one from an auto parts store,or you can remove the alternator and take it to the auto parts store and have it bench tested along with the battery...usually for free...
An alternator keeps the battery charged in a vehicle. In a 2006 Chevrolet Impala when the alternator fails the battery will keep dying and no power will be available when attempting to start the car.
Need more info... How old is it? Do you drive short distances? Does it sit around not driven a lot? Check for a short, bad alternator, or fried battery. If you take the car to an alternator shop, they can usually tell you for free if it's the battery or the alternator.
you could pull off your positive battery cable if it stalls out then you alternator is the problem
the battery will not charge properly
Have it load tested by a shop, most parts stores will load test your battery and alternator for free.
if the battery is dead, there will be no ignition lights etc when u turn the key your headlights would be very dim if on at all. the alternator only works when engine is running, so if alternator is dead it will not charge the battery most auto stores will check both battery and alternator for free if you remove from car and take them to the store
take the car to a repair shop and have them put a battery tester on it. it may be the alternator or the battery the tester will tell