how can I tell if I need a new car battery or a new alternator?

Question

I recently purchased a 1991 Chevy beretta from a private owner, it has been running good for the last 3 weeks despite this cold Chicago winter weather, but all of a sudden today it wouldnt start, it was a -5 degrees today and everyone was tellin me it was the weather that killed the battery, but it wont start period it makes no roaring sound when I turn the key or nothing, I have an alarm, my alarm won't chirp, and my power locks wont lock, my uncle told me the battery was dead and I need to purchase, a new one, but my brother told me it may be the alternator I need, he said he couldnt tell if it was the alternator unless the car was started, I got a jump from my cousin and the car started to make a little noise when I turned the key but still didnt start up, and my alarm was working and power locks then about an hour later my alarm wasnt working no more and the power locks werent working anymore and again the car nade no roaring, so how can I tell if I need a battery or new alternator

Answer 1

this could be a battery failure or a charging system failure.
First take your battery out of the car and take it to get tested. this will require that the battery be charged for at least 2 hours before testing. this will determine if the battery is bad. replace it if bad.
put the battery back into car and start. now take car into have charging system tested. if alternator is bad replace it. there are autozone part stores in the Chicago area that will test both for free.
don't disconnect the battery with the engine running. the alternator will not work without the battery as it requires voltage to generate voltage and disconnecting the battery while running could cause other electrical components the fail!!!!

Answer 2

There was also a battery charging problme with my car. The battery light was ON at the dash board. Even I drived the Car, Car has been stopped after 20Km & battery got totallly dad & I was on the highway. After that I took vehicle to the mechanic, he said alternator fault, I purchased a new alternator. When mechanic cheked the old alternator, he said it is ok, just the carbon type one element is missing/ damaged due to over time. SO purchased the carbon with spring costs only 6$. I returened back the new Alternator which I bought. So please check with mechanic, Is the alternor repairable. As in my case.

Answer 3

It could be a failure of both. The cold will definetly kill your battery, but also, if you have a malfunctioning alternator, that could also cause that.
But its much more likely that the cold is the culprit. You can take your battery inside and leave it overnight. If tommorow you have the same problem, then youre going to need to replace it. When/if you replace it, purchase a battery warmer.
They are around $35, but it will save you so much money.
http://www.jcwhitney.com/autoparts/Product/s-10101/Pr-p_Product.CATENTRY_ID:2006128/p-2006128/N-111+10201+600000917/c-10101/TID-0820

Also, when purchasing a battery, dont go cheap. You want the highest cranking amps you can get. Living in chicago, you need to expect bitterly cold temps, and an investment on a good battery is a must.
I lived in michigan in high school, and i kept buying cheap batteries. I went through $300 in cheap batteries in 4 years. -20 will do that.

Answer 4

I would buy a digital volt ohm meter aka dvom available at radio shack or and big store like sears 15-20 bucks or less checking at the battery for voltage should be 12.2 volts or more(koeo) key off engine off install a good( interstate) battery then recheck with a dvom at battery ( koer) key on engine running should read at least 13.6 or more with all accesories on.if it is not above these readings you will nead an alternator as well otherwise you'll just fubar your new battery p.s.clean tight cables are highly reccomended gl2u brotha.

Answer 5

Hi Ghs, It's is your battery. In that kind of cold..brrrr.. it will kill your battery for sure. Go buy a new one,and try covering you can,and see if that helps some. A Friend.

Clowmy

Answer 6

get a charger and charge the battery or get a jump... but let the other car sit there and charge it for awhile... after the car gets started... disconnect the positive battery cable and see if the car shuts off... if it does then the altenator is bad... if you have an AutoZone in your area... let them check them both

just that simple

Answer 7

most auto part shops will test your battery for free, all you have to do is take it out and bring it in. might as well since you'll need to go there for a new battery if you need one.

Answer 8

most likely your battery is at least very weak......but it did take a slight charge.....from the jump.............make sure your battery terminals are clean & tight........put a charger on it....charge on trickle charge overnight........then you will need a volt meter...connected across your battery terminals.....note the reading....should read 12.5 volts..........if not...you need a new battery....if yes.....start your engine.......note your reading......it should read 13.5 to 14.5 volts........if not......could be bad alternator.......check all wiring,& belt tension.....if still not, replace your alternator...........hope this help,s you.

Answer 9

jump start the car and once you have it running unhook the battary if it stays running then replace the battary if it dies then it is your altinator

Answer 10

definitely needs a new battery. try this, honk the horn to see whether it works or not!