Is it my battery or alternator?

Question

How can you tell if it is the battery or the alternator that is stopping a car from starting???

Answer 1

get it jump started and take it to autozone and get a free charging system check to find out for sure what the problem is.

Answer 2

Could be battery, alternator, starter, or any of several wires if you can't get it to crank over. If it does crank over, but doesn't start, that's a whole 'nother can of worms.

Here's some articles that explain how to diagnose the first problem;

http://www.aa1car.com/library/2002/cm102...

http://www.aa1car.com/library/charging_c...

http://www.aa1car.com/library/battery_ru...

PS, don't listen to the idiots who tell you to disconnect the battery.

And by that, I mean ANYTHING he says.

Answer 3

Jump start the car. Wait until it is running on it's own and then disconnect the battery. If the car remains running with only a slight drop in power, your alternator is OK. The starting problem is your battery.

If you substitute a fresh battery and it runs down in a few days, it is your voltage regulator which is built into your alternator. i.e. your alternator is bed even if the car will run on it. Charging circuit is bad.

Answer 4

The alternator will not stop a car from starting. The battery supplies power to the starter to crank the motor over until it starts. Once it starts, if your alternator is good, the alternator will charge your battery. If your car is clicking when you turn the key, then your battery is low on it's charge. If it was fine the day before and it was driven, then it is losing its power because the alternator isn't charging it. It will die pretty fast. If a car is clicking when the key is turned, check battery, battery cables and starter/solenoid. If it is turning over but not starting, that could be many things. Main things there: compression, fuel, spark, timing, and power. If it turns over normally and not all sluggish and your lights work without being all dim, then your battery is fine and you can expand on the other four I listed. Best of luck!

Answer 5

turn your head lights on if they are nice and bright, have someone watch them and try to start your car. if the light go dem, you have a low batt. or a bad starter, if the lights stay bright you have a bad starter solenoid,nuatrel safety switch, elec. ing. switch. if when you first turn on your lights they areDemn you have a low batt. charge. could be bad alt. or batt.

Answer 6

Charge the battery ,if it takes a charge a shop can do a load test to check for a bad starter and test the alternator for proper out put,about 13.5 volts or more.  

Answer 7

put in a good battery. or load test the battery that is in the car after it is fully charged. when the care is running put a volt meter across the battery and anything over 13 volts is a good alternator.

Answer 8

not sure what you mean..if the battery in holding a charge, its not it..but what about the starter, is it turning over? you have to have a mechanic check them..