alternator question

hello - i changed my alternator n battery last week ( 65 merc montclair ) ... ran great all week, this morning battery died, maybe didn't get belt tight enough ? would she hav been fine all week ? feel lik i'm leaving some vital piece of info out ... hehe ... any help appreciated ... thanx

 

Most obvious is the least obvious.., double check your grounding points, ie; battery at post and at ch***is (check cable for signs of interior corosion also), alternator grounding at bracket (if req'd) and run your wiring to make sure nothings shorted or broken under the insulation, or any terminals have loosened up. Ensure your alternator belt has no more than 1/2 inch play in it (grab it with your fingers and move it up and down vertically).

Your battery can easily get thru quite a few days on its own if you're only using it start the car or with the minimal use of the cars accy's.

If it's a "rebuilt" alternator, it can still be bad right out the box (as can a "new" battery thats been on the shelf for a while), throw a volt meter on your battery, make sure it's fully charged (12.8-13.4 volts), then fire up the engine, hit the alternator with the voltmeter, should read at least 14.2 no load.

 

Follow what sckracing suggested after you have put a full charge on the battery.
We are ***uming that you did check to make sure that it was indeed charging after you installed it.

Some times new or replaced doesn't mean "working" and you have to test/check the items to make sure that they are indeed doing what they are supposed to. It's quite possible that you were able to make short daytime trips for a week just running on the battery without the alternator actually charging and that is my su****ion.

And before changing anything else go back and check the connections to make sure that they are good and make sure that the ground cable from the battery is making contact with "bare metal" on the block and not trying to ground through paint.

 

thanx guys, got my weekend project while grommies r out o town ... let ya know how it turns out n thanx for the reply ...

 

Did you get a regulator as well ????

 

i didnt , i guess i should? or try all else first ?

 

it ran fine for a while cause you were running on just your battery. sounds like your alternator 1)isnt charging or 2) isnt getting the charge back to the battery.

follow what the others said...this is just my 2 cents worth

 

Sounds like a good chance the regulator failed so you aren't getting any charge to the batt. Hopefully you haven't hurt the new Alt or killed the new battery by overdraining.

 

... don't overlook the possibility of a short draining the battery overnite.. perhaps you had enough juice to start all week but it caught up with you the day it wouldn't start.

go buy a digital voltmeter. without one everything else is just a guess.

 

Why did you change the Battery and Alternator in the first place? did you have the old ones checked?

 

What was the reason you changed the alternator n battery for in the first place?

Dead battery don't mean there's anything wrong with the charging system..........Maybe somebody's been out there playing in the car at night listening to music or reading literature and running the battery down............... Do you have a teenager?

Or the lights or ignition got left on?

I would hook up a battery charger and start from scratch, eliminate the obvious before ***uming it's a bad battery or alternator.

 

alritee, fromthe top, ran for cupla days, then batt dead, charge batt, wont hold charge, test batt, she's good, change alt n all good for week or so ... ( still glad i changed her if only for experience cuz i clearly dont know wat im doin but am super stoked bout it) regardless, now, voltmeter n regulater, not that im sure what that is but am looking it up as i type thanx agin, really appreciate advice ... oh yeah groms r 8 n 5 so if they'r draining batt . . . i guess thats for another forum

 

I was test drivin' when I was 5, drivin with the motor on when I was 9

test meter;


Five bucks at harbor freight, fifteen bucks at radio shack. I have five, one in every tool box, one in each car. Guess where I bought them.
1) check battery voltage with motor off. It'll be about 12.
2) check it again with motor running. It'll be about 14 if the alternator is charging.
If it isn't charging, since you have a new alternator, it's most likely the voltage regulator, (***uming you have the correct alternator and it's connected properly) If the alternator is charging, something is draining the battery when the car is sitting idle.

 

As 29Nash said, if you don't have a Multi-meter you need one. Harbor freight usually has one on sale for under five bucks if you are really low buck. Sears also has several that are usually under 20 bucks.

Usually 12.5 volts is considered charged up for a battery just sitting there. 14.2 volts is the desired charging voltage when things are working right.

As I said previously, a car with a good battery can run quite a ways and be started a number of times without a working charging system or even an alternator or generator on the car such as on a lot of short track circle track cars or drag cars. With that you may have made several short daytime trips with the car before you ran the battery down to where the car wouldn't start.

 

start car disconnect positive cable and if it dies your alt is not charging.

 

That's true with a generator, not true with an alternator.

 

sweet sweet ... on it tomorrow ... i better keep a better eye on the lil groms, just in case ... let u guys know what's i find