electrical problem?

[redcoats1976]

went out to the garage this morning and turned the key...nothing.had to go through the backseat to open the trunk and jump start.i tested voltage and it was reading5 volts,but after a short time running it would restart,so i took it to autozone.battery good(less than a year old and tested good,starter good,alternator failed.but voltage regulator and diodes pass and car shows between 13 and 14.4 volts when running.autozone guy says replace alternator,what do you think?

[gtstorey]

How long had the car been setting?

[redcoats1976]

week at the most.i pulled it out saturday and detailed it.had been on a 120 mile trip a couple of days before.

[gtstorey]

I would use a battery charger to fully charge the battery and then check voltage drop when trying to start with a multimeter. And if you can let it set see how much the voltage drops after a full charge for a day or two.

[redcoats1976]

are you thinking a wiring problem?if its an internal alternator issue im thinking about just replacing it tomorrow and getting it over with...kind of odd that it shows between 13 and 14.4 when running,but according to autozone charging system fails the test.tester hooks up to battery terminals if that matters.

[morepowerjoe]

Originally Posted by gtstorey

I would use a battery charger to fully charge the battery and then check voltage drop when trying to start with a multimeter. And if you can let it set see how much the voltage drops after a full charge for a day or two.

I'm with him on this one but I did have a battery that did the same thing yours is doing. It would start up to like three days out but let it go a week and it was a no go. Took it to Autozone and it tested fine but I new it was the battery so I went ahead and got a new duralast gold and no problems since and I just had to replace that one after four years. But like gtstorey said I would put it on a charge for like a good day.

[gtstorey]

Originally Posted by redcoats1976

are you thinking a wiring problem?if its an internal alternator issue im thinking about just replacing it tomorrow and getting it over with...kind of odd that it shows between 13 and 14.4 when running,but according to autozone charging system fails the test.tester hooks up to battery terminals if that matters.

The only time I trust parts store on warranty testing is when they tell me the part is bad and hand me a new one.

My steps are a test of the battery under load (voltage drop) followed by testing if the battery just won't hold a charge or if there might be a high parasitic load pulling it down (such as a module that isn't powering down correctly).

I have seen batteries that would just slowly drop voltage with nothing on it but a voltmeter.

[chevy pilot]

Originally Posted by gtstorey

I would use a battery charger to fully charge the battery and then check voltage drop when trying to start with a multimeter. And if you can let it set see how much the voltage drops after a full charge for a day or two.

+1

[ariZona28]

Originally Posted by redcoats1976

..had to go through the backseat to open the trunk and jump start.

You are aware that you can jump start our cars at this terminal under the hood, right? Might not be enough to start a stone dead battery but it should get you enough juice to open the trunk.

[redcoats1976]

yup.but i park on the left side of a two car garage and the other cars battery is on the right side...somedays you just cant buy a vowel.gonna take the battery out of the car tomorrow and charge it all day and leave it out for a few days and see if theres a voltage drop when not connected to the car(i hope there is,dont like electrical gremlins)

[redcoats1976]

it started this morning ,battery is now disconnected from the car and on deep cycle charge.chargred it 8 hours and it now reads 14.7 volts on the DIC and starts right up.voltage tester shows a little over 12 volts.im going to let it sit a few days in the garagwe and see what happens.

[redcoats1976]

ok,tested the battery in the car,it reads12.5 on my old sears tester.when i start the car the reading goes to 14.5.im going to subtitute the wifes car battery and see if the voltage at the terminals goes to a lower reading.if so im going to replace the battery and see what happens.sound right?

[gtstorey]

What happens to the voltage when actually trying to crank the car? That is going to tell us something about the health of the battery. You can floor the pedal to put it into flood clear mode to keep it from actually running.

[redcoats1976]

put the wifes battery into it,same results.im going out of town for a few days so the car will be sitting.14.7 is on the high side,will it be ok to run the car like that and see if the voltage goes down after a long trip,say 100 miles? according to autozone tester.doides pass voltage regulator passes but charging current fails.according to the DIC and my voltage meter its charging like a bandit though.