Battery or alternator?

[johnnycharger]

Hi guys
my battery keeps going dead on me. if I can jump start and drive it home but then not start it again without being jumped(or hooked to the battery tender... is that a sign of a dead battery and if the alternator is OK? If I have it on the tender overnight it is good for 2 or 3 starts before it is dead again.

[nascarxx29]

Take battery out get full charged and load tested out at auto parts store if its more than 3 years old replace it.Then you can sort out if its the alternator regulator or a connection problem

[Back N Black]

Do you have a multi meter? check with engine running, should have 13.5 to 14 volts at the battery.

[johnnycharger]

Take battery out get full charged and load tested out at auto parts store if its more than 3 years old replace it.Then you can sort out if its the alternator regulator or a connection problem

My battery is 4 years old but I am hoping not to buy a new one if it is still good....

Do you have a multi meter? check with engine running, should have 13.5 to 14 volts at the battery.

I have a meter and can try this tomorrow after charging it overnight.  Currently if I put the meter on it states over 12v but as soon as I try to start it the volts drop to 3-4 volts and it doesn't crank...

[A383Wing]

sounds like bad battery or corroded or bad cable connections at the battery terminals or on the engine

[johnnycharger]

If it is the battery.... what CCA rating do you guys recommend? Currently I have 810.

[lukedukem]

i had my car do this also. it wouldn't start one day, and i had to jump it. kept doing it. turned out it was a bad ground. i cleaned my battery connections and the connection where the ground went and i fired right up. not sure if your is the same issue, but its a cheap easy test to do.

Luke

[johnnycharger]

Do you have a multi meter? check with engine running, should have 13.5 to 14 volts at the battery.

Just checked with it running and the voltage at the battery is he same as when it is off. About 12.5

[Back N Black]

sound like a voltage regulator issue. Could be bad ground, wiring or the regulator.

[A383Wing]

sound like a voltage regulator issue. Could be bad ground, wiring or the regulator.

could be bad alternator also

[nascarxx29]

Once you establish battery is good .check grounds and power to alternator and regulator,And bulkhead and amp gauuge connections .alt could have a bad diode or slipping belt.Take out alt to parts store for a free evaluation

[johnnycharger]

Take battery out get full charged and load tested out at auto parts store if its more than 3 years old replace it.Then you can sort out if its the alternator regulator or a connection problem

My battery was more than three years old so I pulled the trigger on a new Interstate Megatron and that seems to have fixed it. Fired right up over a dozen or so times. Cranks noticibly faster now too!
Thanks guys!

[Back N Black]

Did you check the volts at the battery after you installed the new battery? With the new battery being much stronger than the old one, you still could be running just on battery power.

[nascarxx29]

Do you have 13.5.   14 volts at battery cables now  and check your amp gauge to see if its indicating charging.I had just been thru similar problem battey had a bad cell.It was easier to start by having battery  evaulated.

[johnnycharger]

Did you check the volts at the battery after you installed the new battery? With the new battery being much stronger than the old one, you still could be running just on battery power.

I checked it again both running and not. I got about 12.5 still each time.

[nascarxx29]

Is your battery voltage same as running or not 12.5 .check it with lights on at idle
you might have a bad diode in alt.And giving it gas does amp gauge show increase of charging.you want 13.5 or slightly higher

[Pete in NH]

Hi,

I would say then your alternator system is not producing any output and your new battery will soon be as dead as the old one.

Some time spent doing some actual trouble shooting will save you money, rather than changing parts until things work again. I didn't see that you mentioned what year car you are working on. There are two common alternator/regulator systems and each one has slightly different test procedures. So, first question what year car and is it the stock alternator/regulator system for that year?

[nascarxx29]

He should pull alternator  go to a parts store for free they will test it.And as you find out you might to change regulator.If its original .


Seen a older post mentioned 70 flat black charger with tan interior .If thats you you should have a 2 field alternator and flat type voltage regulator

[A383Wing]

Did you check the volts at the battery after you installed the new battery? With the new battery being much stronger than the old one, you still could be running just on battery power.

I checked it again both running and not. I got about 12.5 still each time.

12.5 volts when engine is running means the battery is NOT being charged.....you will have another dead battery if you don't find out why it's not being charged

[johnnycharger]

This can't be helping my alternator any.

[johnnycharger]

It is a 70 charger. There are 2 electrical connections on the alternator plus what looks like a ground lug which has come free inside and I can move around.

[birdsandbees]

That's not a ground lug.. that's your "B" lead to the battery. The '70 has dual Field connections, which are the other two wires. Looks like someone wrenched on that B lead nut without holding the post nut. Probably an easy fix if you have a local electrical shop that rebuilds alternators and starters.

[Pete in NH]

You can try tightening up that output stud bolt. Before you do anything disconnect the negative battery cable from the battery. I would take the alternator off the engine as it will be easier to work on. There should be two nuts on that output stud, one holds the wire ring terminal on and the inner one keeps the stud tight internally. After removing the outer nut you may be able to tighten the inner one. If it just keeps spinning you will have to disassemble the alternator to tighten it.

This loose stud may or may not be the complete problem but you certainly need to correct before going any further.

[johnnycharger]

The alternator had a lifetime warranty on it so I swapped it out. I am now getting 15v at the battery when running and 13v when off.
Thank you all for the help#

[myk]

Isn't that kinda high?

[69wannabe]

Seems a little high to me too, may also need to replace the regulator to get the voltage somewhere between 13.5 and 14.5 while the engine is running. Just thinking, when you first start the engine and check the battery voltage it may be a little higher like that until it fully charges the battery and then it will drop back down to 13-14 volts. I may be wrong tho.....

[A383Wing]

also depends on if he's using a good quality meter or a cheap one from China

[johnnycharger]

I am using a good fluke meter. I checked it immediately upon firing it up. I will run it longer and do more checks to see if it is consistently high.

[nascarxx29]

Could be voltage regulator acting up or not grounded if readings are to high 14.5 volts ok

[johnnycharger]

After running it a bit it is now reading at 14.4/14.5 while idling.
(Sorry for the delayed response)
Thanks for the help with this guys!