If the voltage metere is moving up and down there a good chance that its the alt. You can also place a volt meter on the battery while the motor is running (with every thing off), look and the voltage, then turn your A/C on high, turn your lights, wipers, radio ON, if the voltage goes below 12.5, there a good chance that it is bad.
How to Tell If Your Car Alternator Is Bad Check related link below…
A bad belt, a bad regulator in the alternator or bad brushes in the alternator.
you could pull off your positive battery cable if it stalls out then you alternator is the problem
Start the car, unplug the battery the alternater should power the car. If it dies the alternator is bad. You can also get it checked at any parts store.
The quick easy method for determining a bad alternator or at least to find out if it is charging, while the car IS running remove the negative battery cable from the battery, if the car stalls then you need to have the alternator service inspected.
Get engine running. While the engine is running disconect the POSITIVE termninal from the battery. If the engine dies, the Alterntor is bad.
Perhaps thids might help... http://wiki.answers.com/Q/How_do_you_tell_if_the_battery_or_the_alternator_is_bad
The best way is to drive it to your nearest auto parts store and have it tested. You can test it somewhat yourself. Start the engine and use a volt meter to test the voltage that is being supplied by the alternator for the battery. If it is less than 13.5 volts the alternator is bad.
bad alternator, bad voltage regulator, bad battery, bad connections.
The alternator is belt driven and so is the water pump but that is where the correlation ends. There is no way a bad alternator could cause a water pump to go bad unless the alternator pulley was warped. Then there is a small chance.
alternator is bad
Spark Plugs do not affect your alternator. As long as your engine is running then it should be charging unless your alternator is bad
a bad ground wire can ruin an alternator by not completing the circuit
Start the vehicle then disconnect the battery. If the motor dies, you probably have a bad alternator.
A bad alternator will not give proper power to the vehicle. Dim lights, buzz in the stereo or a dead battery could all be causes of a bad alternator.
Start engine and measure volts at battery, it should be at least 13
bad alternator cable/corrosion bad battery
it can be caused by a bad alternator
No, if it is bad of course it will not work.
Do you have a amp??if you do it could be that the amp is sucking alot of energy from battery.And I'm guessing u have a stock alternator take your battery to autozone tell them if they can charge it is free and they will tell you is your Battery is bad.. If you don't hav all this maybe you hav a bad alternator and it wont charge ur battery maybe u need a new alternator...,just take your truck to autozone and tell them if they can check your battery and alternator from there you will know what's wrong hope this helps alot I had the same thing and it suck
Many possibilities. Check in theis order: Bad battery connections? Bad battery? Loose alternator belt? Bad alternator connections? Bad alternator? (Test at auto parts store.)
Bad alternator? Bad voltage regulator? Bad Battery (won't take a charge)? Bad fusable link? Loose or corroded battery cables?
Turn car on remove positive battery terminal if car turns off alternator is bad
Take the belt off and spin the alternator by hand. If you hear a grinding noise, like sand rubbing on metal, its probably going bad. Also try to wiggle the pulley up/down/left/right. If it wiggles, the bearings are going bad. Of coarse you can always wait until they get so bad they shatter and the alternator wont spin at all, like i did. :(
If it is makeing a noise or is not putting out at least 13.5 volts it is bad. Take the car or the alternator to an Auto Parts store and have them load test the alternator to be sure.