Battery isn't getting charged on my 82 F150

[Big John Hance]

I changed the voltage regulator and put on a new battery. Right before I bought the truck in July, my uncle installed a rebuilt alternator. A few weeks ago I kept having problems with my battery dieing, and I've come to the conclusion that it isn't being charged. I think it's a problem with the alternator but I don't know much about this stuff so I'm not sure. Is there anything that might be drawing power from it after it's off and have any of you guys experienced this before?

[unclebubbles]

Several things can cause an alternator to stay energized after the engine is turned off. A shorted diode can cause the stator windings to be energized and draw current. A bad regulator can cause the field to stay energized. If you have a multimeter, you can check for current draw. Or you can touch a screwdriver or wrench to the back of the alternator. If it has a strong magnetic pull, its staying energized. If you dont have a meter, you can take the alt off and take it to an auto parts store that has test equip. and most will test them no charge. You can also leave it on, drive it to the auto parts store, and let them test the battery/charging system. Most stores have the equip to do this. Another seat of the pants test for older vehicles, is to start the vehicle, then take a battery cable off. If it stays running , the alt is putting out, but you dont know how much voltage or current. Its not reccommened to do this on newer vehicles with ecm`s, it can damage the computer. Of course there are other things that can cause current draw too. Radios/accessories/alarm systems....ect. which can be disconnected to isolate a problem.

[MT-2500]

Originally Posted by unclebubbles

Several things can cause an alternator to stay energized after the engine is turned off. A shorted diode can cause the stator windings to be energized and draw current. A bad regulator can cause the field to stay energized. If you have a multimeter, you can check for current draw. Or you can touch a screwdriver or wrench to the back of the alternator. If it has a strong magnetic pull, its staying energized. If you dont have a meter, you can take the alt off and take it to an auto parts store that has test equip. and most will test them no charge. You can also leave it on, drive it to the auto parts store, and let them test the battery/charging system. Most stores have the equip to do this. Another seat of the pants test for older vehicles, is to start the vehicle, then take a battery cable off. If it stays running , the alt is putting out, but you dont know how much voltage or current. Its not reccommened to do this on newer vehicles with ecm`s, it can damage the computer. Of course there are other things that can cause current draw too. Radios/accessories/alarm systems....ect. which can be disconnected to isolate a problem.

Removing the battery cable when running is not safe on anything with a alternator.
But removing the battery cable when sitting for a day or two is a good test to see if the battery is weak or a amp draw is killing the battery.
Cable off and battery still goes dead when sitting the battery is bad.

[Big John Hance]

I took it to the local Auto Zone two weeks ago and had them test the alternator while it was in the truck. The tech came to the conclusion that it was putting out power just fine and he didn't know what the problem was.

[MT-2500]

Originally Posted by Big John Hance

I took it to the local Auto Zone two weeks ago and had them test the alternator while it was in the truck. The tech came to the conclusion that it was putting out power just fine and he didn't know what the problem was.

Was that a trained auto repair tech or a trained parts person?:
But at least they told you like it is.
It was putting out power but was it the right voltage and was it carrying a full load?
Is the battery going down when the truck is running or after sitting a day or two?

[unclebubbles]

Removing the battery cable when running is not safe on anything with a alternator.

Didnt say it was safe, said it was a seat of the pants test. But in 40 years ive never seen it damage an alternator or regulator, or anything else for that matter. And i didnt say i do it, i have test equipment, but everybody doesnt. I have seen people do it on newer vehicles and fry the ecm though.

Big John, if you dont have a meter, make sure no interior lights, radios, or anything else is on, and with the truck not running, after its been sitting a while, take the neg cable off and touch it to the batt term. If you get any spark at all, somethings drawing current. If you get no spark at all, suspect a bad battery, bad alt, or bad wiring/connections somewhere. Ask them to retest the alt, this time turn everything on in the truck, lights , fan...ect. If its not load tested like MT_2500 suggested, its not an accurate test.

[Big John Hance]

Originally Posted by MT-2500

Was that a trained auto repair tech or a trained parts person?:
But at least they told you like it is.
It was putting out power but was it the right voltage and was it carrying a full load?
Is the battery going down when the truck is running or after sitting a day or two?

It's getting run down while the truck is running, which is why I suspect it's an alterantor problem. It has a brand new battery so it charges itself a little while the truck is off, but I have been charging it with a regular battery charger until I get it fixed.

[MT-2500]

Originally Posted by Big John Hance

It's getting run down while the truck is running, which is why I suspect it's an alterantor problem. It has a brand new battery so it charges itself a little while the truck is off, but I have been charging it with a regular battery charger until I get it fixed.

Does it have a separate regulator or one built in alternator?
A good repair shop and some parts places can test the alternator output to see what is is doing.
If AZ could not find the problem shop around a little for a place that can.
MT

[Big John Hance]

It has a separate regulator which I have already replaced.

[dstrick32]

I believe I would invest in a digital Muti-meter and do some testing on my own. You can check for any drains and all your volt reading at each point.

[MT-2500]

Originally Posted by Big John Hance

It has a separate regulator which I have already replaced.

If the battery runs down running it is more than likely the alternator or wiring.
A good volt/ohm meter will tell you if it is charging good or the wiring is good.
Most repair shops can run a on the truck test of charging system to see if thee alternator is charing or discharging while running.
Or a volt meter reading will tell the story.

[Big John Hance]

I will try to take it to someone and have it tested. I can't really afford to buy any kind of meter right now. I just put in a new clutch and that's all the money I'll have for a few weeks.

I'll try Advanced Auto Parts or somewhere similar.

[Big John Hance]

Well guys, I finally figured out the problem.


The alternator belt was really loose, so it was slipping. I tightened it up yesterday and it works beautifully.

[dstrick32]

Glad you found it, kinda figure it was something in /at the alternator!!

[Big John Hance]

The belt is still a bit loose, but it's getting charged so I'm not going to worry about it.