Battery or Alternator

[The Dude Abides]

So im almost 99% sure the battery crapped out on my taurus. It will start with a jump and when its running it puts out 14.50 volts on the voltimeter. When i turn on the headlights and the heater it still puts out 14.50 volts which leats me to believe the alternator is doing its job. But the battery doesnt seem to be holding a charge. After i jumped it it started 4 times after then and then it was dead. I let it run for about 15 minutes after i jumped it. While it was running the interior lights would flicker alittle bit makeing me think the alternator might be at fault. Im new to useing the multimeter but i know i hooked it up right. Any suggestions.

[bheinen74]

Alternator is bad, its putting out too much voltage, (bad voltage regulator in it) and it has cooked your battery. Batteries are not meant to be charge more than 13.5 V. The alternator has cooked the lead acid cells.

 

 

-you will need both a battery and a alternator that only charges to 13.5v to fix your issue.

 

You can unhook every cable to the battery, and put your MM tester on the pos and neg of the battery, and if you hold the tester on it, the volt on the batt will continually drop, 12.5, 12.4, 12.3.12...,11.5.11.4.11.3, etc down til like 10.0v its dead due to overcharging.

[The Dude Abides]

Most of the batterys i have checked run 14.50 when charging on the car.

[TheSubaruJunkie]

Yeah my alternator charges at 14.4 volts. Dont worry.

 

Put your multimeter on the battery and check voltage with the engine off. Start the engine, let it run and idle... then shut it off and check voltage. See if voltage on the battery has increased or not.

 

From what you say, it sounds to me as if the battery is bad... it should be holding a charge if 12+ volts are being supplied to it.

 

You can also do a load test on the battery to verify if its bad or not, but its hard to do with just a multimeter. Its best to have a shop check that though.

[porcupine73]

Make sure all ground connections are tight too. Load test the battery. If it's a normal starter battery more than a couple years old, if it went dead a few times for any reason, it might be shot. Starter batteries do not like to be discharged deeply, it greatly reduces their lifespan every time that happens.

[daredevil1166]

I'd check to see if there is a current draw on the battery when parked and off. There may be a little but if it's too much it'll run your battery down.

[The Dude Abides]

Ok update.

 

Jump started the car tonight and it ran fine. Had it running for 30 minutes while i looked over certain things made sure a couple of things were ship shape. Turned the car off then went to turn it back on (click) nada. So in saying this. The alternator is good enough to keep all the lights, interior lights and everything else powered when the car is running. But the battery probally has a dead cell causeing it not to be able to get charged. Or is it possible the terminals and wires are so crudded up from neglect that there not allowing current to get back to the battery to charge it. Theres a pretty good onion growing on the positive terminal but its been six months since ive cleaned up the last one. 99.9 percent sure its the battery but who knows. I need to clean up the electrical connections so that will be my sunday project.

 

On a side note, anyone know why my headlights and interior lights might flicker every once in a while.

Edited August 27, 2010 by The Dude Abides

[TheSubaruJunkie]

Replace your battery cables. I have seen corrosion work its way into the cable, you'd never notice it because the corrosion gets under the insulation and renders the cable useless.

 

New cables are cheaper than a new battery.

[The Dude Abides]

Replace your battery cables. I have seen corrosion work its way into the cable, you'd never notice it because the corrosion gets under the insulation and renders the cable useless.

 

New cables are cheaper than a new battery.

 

So i should check out the cables before i second guess the battery.

[daredevil1166]

I think you're getting waaay ahead of yourself.

 

Just take the car to an auto parts place that can test the battery.

 

Or buy a cheap Harbor Freight load tester.

 

It's very simple to check things without all this guessing.

[TheSubaruJunkie]

So i should check out the cables before i second guess the battery.

 

No, i am almost sure your battery is still bad. But when you get a new one, buy new cables and install them as well. Its probably only $10 for a set of cables, and it'll be worth it.

[The Dude Abides]

Yea i hear ya, this thing starts pretty slowly so im sure the cables are corroded big time. Will be worth it if we have another bad winter. 850 cold cranking amps baby. Should get a new battery in a couple of weeks.