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new dead battery?

zimmy

Jedi Knight
Offline
so, i put a new battery in a week or so ago,
drove a couple days, and now its dead...boohoo!
so i reluctantly push started it and made it home..etc.
soon as im home i try to start with NO luck at all...
tick tick...
it appears my alternator is working since the car runs
once started.......the alternator is almost new also...
all wires appear connected properly....

one thing though.....
my radio used to turn itself off when i turn off the key...
now it doesnt, so i remove the face to be sure....
could my switch be involved? my starter is run from a dash button, but the switch turns on the fuel pump,etc...

i thought since its been a little slow on here lately,
u guys would enjoy troubleshooting this...should b easy...
ill keep u updated........zimmmmy
 

Sarastro

Obi Wan
Gold
Country flag
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This isn't at all unusual. Even a little bit of resistance will prevent starting, but won't affect the operation of other things that don't draw nearly as much current. Make sure all the battery connections are tight, uncorroded, and REALLY clean. Also, all the connections between the battery and the starter, which may have been disturbed and loosened inadvertently when the new battery was installed. If you can push-start and drive the car, the battery isn't totally flat.

If the radio stays on when you turn off the key, and it didn't previously, probably other parts that should be switched off are staying energized, too. That, of course, can drain the battery and might be part of the problem. Whether related or not, you obviously need to fix it.
 
OP
zimmy

zimmy

Jedi Knight
Offline
im all over it steve!
its 60 degrees out and sunny!
ive got 11.7 volts at the
battery, both wires on the alternator,
and everything in between.......
still workin on it......z
 

Speedy_Pete

Jedi Trainee
Offline
I'll add my 2 cents here... seen a similar problem recently.
Battery was tested and found to be good, same for alternator. After giving it a thorough check over the problem was found to be a loose belt. More specifically, the mounting bracket on the alternator had cracked (almost invisible to the eye when in situ), and was moving when under load. Not enough to warrant screeching from under the hood, but enough to prevent the battery from charging.
Unlikely, I know, but perhaps worth a check?
 
OP
zimmy

zimmy

Jedi Knight
Offline
i put my voltometer on it and get 12.66 volts
when revved......appears the alt is working fine...
i DID mess with and tighten some connections...
hopefully all is well tomorrow.........z
 

ecurie_ecosse

Luke Skywalker
Offline
zimmy said:
i put my voltometer on it and get 12.66 volts
when revved......appears the alt is working fine...
i DID mess with and tighten some connections...
hopefully all is well tomorrow.........z

And is all well today Zimmy? /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

Loose or dirty connections are the culprits frequently to blame when this happens. /bcforum/images/%%GRAEMLIN_URL%%/driving.gif

Stuart. /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 

fmichaels

Jedi Knight
Offline
here's my 2 cents. if you installed a new radio, the orange wire from the radio usually requires a constant 12V source. It maintains the station pre-sets and clock as well as other memory functions. Therefore, this could be draining the battery. Normally, the draw from this load does not affect the battery or everyone's car battery would be dead. If the car is completely shut off, and you remove the positive cable from the battery and tap the post with the cable and get a spark, you have a current draw somewhere in the car. It could also be something that is shorted or shorting. if you can't see a spark when you check the cable to post, try it at night when it is dark. the spark may not be large enough to see in daylight. if the problem is persistent and you can't find it, you can consider one of those battery disconnect switches to prevent current draw when the car is idle. just some thoughts/ramblings.
 

Billm

Yoda
Offline
12.6 volts is NOT correct! Your alternator should be putting out between 14.2 and 14.7 volts to be doing anything. I would say that one (or more) or your diodes is shot or if you are lucky your voltage regulator just needs adjusting. 12.6 volts may run your car but won't charge the battery.
Bill
 

Sarastro

Obi Wan
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You very well might be right. It's also possible that, if the battery is nearly discharged, it's holding down the system voltage until the alternator charges it more. I'd suggest charging the battery with an external charger, checking the output current with the switch off (to make sure it isn't the switch staying on somehow), and that should answer the question.

A battery charger is a great thing to have when you deal with LBCs. I still have the cheapo Sears one I used on my Triumph back in the 60s. It still gets used, too.
 
OP
zimmy

zimmy

Jedi Knight
Offline
i started the cdar today.........went to get some gas down the street, and when i get back my battery says 11.9 volts..
i think ill take the alt back to oreillys and have it checked tomorrow........otherwise, ran pretty good ; )

so , i should get 14 volts when charging?
i cant remember............z
 

Dave Russell

Yoda - R.I.P
Gold
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You should get around 14.5 volts when the alternator is charging. Did you check - tighten the belt tension as suggested earlier. This would be the most likely cause of the problem.
D
 

wolfman

Senior Member
Offline
I think 14.7 is too high. I think 13.7 - 14.2 are good numbers. Anyway, I just copied the following "The alternator produces electricity and delivers this electricity to the battery and maintains a full charge at all times. If the voltage produced by the alternator goes above 13.5 - 14.5 volts, the battery will be ruined very quickly. It's the job of the voltage regulator to keep the output voltage between the 13.5 - 14.5 volt range.

If the battery voltage goes below 13.5 volts, the voltage regulator sends current to the field terminal and allows the alternator to start charging. Current will then flow into the battery and bring it up to full charge. If the voltage goes above 14.5 volts, the voltage regulator shuts off the current to the field terminal and keeps the battery from overcharging and cooking itself. This is how the voltage regulator controls the alternator output.
 
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