Battery or alternator ?

[Muddyone]

So ive had a flat battery twice in the morning now, one night i had just come from about a 45min drive on the highway so i figured it should have been fine but in the morning it was dead. Car seems to run fine apart from a little bit of a whining sound when on the gas. How can i tell if i need a new alternator or just a new battery? Are there any tests i can run myself?

 

[joey]

Do you have a multi meter?

If yes, then with the truck off read the batter level (probably dead)
Then with the truck running, read the batter level...

Or you can also stop by any auto parts store and they should be able to test for free.

Do not remove the battery cable while the vehicle is running.

 

[fire1427]

Do you have a volt/ohm meter ???

 

[Muddyone]

hmm i dont think i do ill have to go buy one... what should it be at when i do?

 

[joey]

With engine running 13 - 15 volts

Engine off no less then 12 volts.

 

[Muddyone]

thanks Joey, im going to check it today and see if I can get this fixed....lol

 

[Muddyone]

So ive replaced the battery and itll start once and then not again for the day, even if ive just come off the highway... so im thinking its gonna be the alternator now, so is this hard to replace or costly. I had just put on a new belt and washed then engine a while ago so im assuming that i fried it at that point?

 

[joey]

Any chance you put the belt on wrong? Also heavy pressure washing of the alternator, then starting and driving off could be ******* it.

I would still test it... take it down to your local auto parts store and have them test the alternator... you can just remove it and have them test.

 

[Muddyone]

Joey you are right as i had a VM hooked up to the alternator and it says its putting out 14amps, but it does say that there is something drawing power when i have nothing on. Ive not added any mods to the car eather... so i donno what is wrong with it now. they only thing that i can think of that could be drawing power is that i blew the subs in the back and have disconected them but i was already having these issues before that. Any ideas... or tests?

 

[joey]

My thoughts would be if it is having a draw on the power... start removing fuses until it is no longer drawing power.

That should narrow down the search.