Battery drain / alternator on the way out?

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Dukester

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First off, finally found a place where it looks like I can start getting some decent info on my 2002 LS V8.

Secondly, here's my issue. The battery went dead during a recent coldish snap (hey this is Texas, it was sort of cold). Battery voltage was down to about 6-7 volts. I didn't think much about it and I went ahead and replaced the battery. After installing the new battery I checked the charge voltage and it was approx 14 volts with the engine idled up some. At the time I didn't pay much attention, just wanted to make sure the alternator was working.

Well fast forward a week and now the battery is dead again. Voltage of about 8 volts and this time I go ahead and charge the battery. Which is not so easy because I have one of those super smart [insert sarcastic face here] chargers and it kept cutting off because of the low voltage. But I get the battery charged and now I can start the car. After topping the battery off, I check current draw with the car off and its about 10 mah, so that seems to be fine. Check the alternator output again and I'm paying attention this time. Alternator seems to run 13.3 to 13.8 idling and then 13.9 to 14.3 at driving rpms.

So if I can rule out excessive current drain with the car off and the battery seems to be fine, my next though was to go ahead and replace the alternator as the charge voltages do seem to be a bit low. Does this sound reasonable or am I overlooking something simpler?

Thanks,
Duke
 
hmm..offhand, those alternator #'s seem to be within spec.

Question: When you took those readings, particularly the ones at 2000rpm or so..did you ensure you had high beams and A/C on? If so, and you still had 14.3, I'd think the alternator is fine.

When my alternator went south earlier this year on my 2002 V8, I had low 12's at idle, and at best..12.7 to 12.9 at 2000 rpm's.
 
check this out, first you can get both of them tested. next I would look to see if something is draining your battery with the car off. I have done this numerous times. I somehow manage to turn my dome light on with the dim switch, well guess what, my dome lights dont work and I havent bothered to change them, so in turn I accidently apply power and the next morning my battery is dead, check the dimmer switch and sure enough I did it again.
 
The alternator numbers are within the low end of the spec. From talking to the tech at the dealership the mid 13's at idle are on the low nominal side.

I've already checked that the power draw with the car off, I measured only 10 milliamps (with the trunk light unplugged, 45 mah with the light plugged in).

There just aren't that many options, if its not drawing power while sitting and the battery is good, then what to do?

Duke
 
How are you testing the power draw, the trunk bulb should draw .74 amp (740 mA) so the numbers you are getting sound too low. Any aftermarket electrical items installed, remote starter, power amps, etc.? If not, I would say that something draining the battery with the key off is unlikely.

Both the alternator and battery need to be tested under load. If you're getting over 14 volts with headlights, a/c and stereo cranked the alternator's probably ok. Open circuit voltage is not a reliable test for a battery, even though it's new you could have got a bad one. You'll need to pull it back out to have it load tested.

If they both check out, then I would start looking for a bad connection somewhere.
 
And as an aside..I had a buddy with a BMW who had similiar issues. When he had the alternator and battery tested at Advance, everything was within spec. It wasnt until the BMW dealership used their computer, and performed their load test, did it determine that he had a "marginal, intermittent" alternator problem. Alternator and battery were replaced, and he hasnt had the issue since.
 
Im having this issue with my 2002 lincoln LSE V8.. had a new battery put in a month ago and left wife stranded. So i chrged batt all night and new batt. has red eye now so took back to advance auto to exchange.. Now im concerned about some sort of draw.. Alt chrging app. 14 volts.....
 
2002 lincoln lse battery draw?

Im having this issue with my 2002 lincoln LSE V8.. had a new battery put in a month ago and left wife stranded. So i chrged batt all night and new batt. has red eye now so took back to advance auto to exchange.. Now im concerned about some sort of draw.. Alt chrging app. 14 volts.....
 
Re-re-check the alternator. I've had one on the LS that was just intermittent. I rigged up a voltmeter to the cig lighter with a gutted cheap charger and drove around. You can also buy little plug-in voltmeter.
 
My alt went bad last summer, and I never got a single bad voltage reading with my DMM. I wasn't having the battery drain issue, but just wanted to put it out there that alts can be intermittently bad.
 
battery draw on lincoln lse

I drove car for a week and realized lights would dim and heater fan motor would drop at idle and when u hit the gas lights would brighten and fan speed would increase soo came to conclusion their wasnt a draw just not enough charging. So vehicle was using too much of the battery so I replaced Alt. and let me say this. Ive been a mechanic my whole life and that was the worst alt. job ever. Its located on bottom right of engine and can only be accessed thru a small opening on bottom of car after removing small access cover. That engine is packed in that compartment sooo tight..Ugghh However it fixed my problem and thanx for the feedback Gents..
 
twood30 said:
I drove car for a week and realized lights would dim and heater fan motor would drop at idle and when u hit the gas lights would brighten and fan speed would increase soo came to conclusion their wasnt a draw just not enough charging. So vehicle was using too much of the battery so I replaced Alt. and let me say this. Ive been a mechanic my whole life and that was the worst alt. job ever. Its located on bottom right of engine and can only be accessed thru a small opening on bottom of car after removing small access cover. That engine is packed in that compartment sooo tight..Ugghh However it fixed my problem and thanx for the feedback Gents..
Click to expand...


wow, good to know, i have the same problem as OP, + this...

this happened last week too, car died after sitting for 5days.
new battery bought 2months ago or so, same alt... alt tested fine
 
Im having the same problem.. its like somethings draining it.. so that means its my alternator.? Thats what everyones fix seemed to be?
 
jrocc said:
Im having the same problem.. its like somethings draining it.. so that means its my alternator.? Thats what everyones fix seemed to be?
Click to expand...

your problem is not the alternator if your car will start back up right after driving it for a while, but will not start up if the cars has sat for a period of time.

if the alt was bad, then it would not charge the battery while you where driving and the car would die and stay dead, it seems like something is draining your battery.
 
1LoudLS said:
your problem is not the alternator if your car will start back up right after driving it for a while, but will not start up if the cars has sat for a period of time.

if the alt was bad, then it would not charge the battery while you where driving and the car would die and stay dead, it seems like something is draining your battery.
Click to expand...

There is an exception to that rule. Sometimes certain failures of the voltage regulator and/or shorted diodes in the alternator can cause it to actually discharge the battery while the car sits.

That said, I don't at all think that the alternator is jrocc's problem. His problem is either the headunit or the way it is connected.

Good trouble shooting would be to pull the fuses going to the headunit and see if the problem goes away. If so, at least you narrowed it down some.
 
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