Alternator bad?

So last week I pulled my battery out for a day to use on another vehicle. One day after putting it back in the charge was dead. I was able to jump it. It ran idle for about 5 minutes then abruptly stoped. When I turned the key nothing. I jumped again and drove it for about 10 minutes but when I came back it idled low and shut off again. Now I cannot jump at all.
My assuption is a bad alternator..yes I have plenty of gas.

I have a parts CJ5 that I can begin swapping out but wanted to check before I started that to see if maybe I'm missing something.

Thanks

 

Do you have a voltmeter? What is the voltage at the battery when the engine is running?

 

I've had two very similar situations (in other vehicles) that turned out to be a bad battery in one and a short in another that ended up being an ignition wire shorting on a choke cable.
Both produced the sudden stop situation.

 

try with the engine running put a screwdriver on the back of the alternator, if it isnt magnetic then its shot, sometimes they can still be magnetic and shot tho

 

Check the output with a voltmeter and post up the results. Would be better if you could test with a volt meter and the output with an inductive ammeter but most people don't have the latter. Also, check the voltage of the battery before and after with the results of the charging voltage. Maybe we can help pinpoint the problem. Also check basic things like corrosion on the cables, terminals, etc. Often overlooked and often the issue. Is this a serviceable battery? (removeable caps) if so check the electolyte level in the cells. If low add filtered bottle water. NOT drinking water. The minerals in regular water can wipe out the cells.

 

x2 on the distilled water.

 

Great suggestions! I will have time to check voltage later this week and will post results. Cables and terminals are fine. This Friday is jeep work day while my wife is doing the Black Friday work day Thanks again for the responses...

 

One way to test an altenator is to get it running, rev it up a time or two to give the altenator a chance to get the tickle it needs to operate then disconect the battery and see if it keeps running. If it dies right away, the alt is not putting out...assuming all the wiring is good. If it keeps running, turn the headlights or heater fan or something that will create a draw and see if it stays running. If it dies with a little load put on it, it is probably not putting enough to charge your battery.

Double check all your wires because you said you pulled it out and put it back in and this started. Problems can often be traced back to the last thing you did. It's not a dig on you, just a fact

 

For $3.49 you can get a voltmeter at Harbor Freight

http://www.harborfreight.com/7-function-digital-multimeter-90899.html



It may not be perfect, but it will go along way toward diagnosing alternator issues.

 

Ok guys so at this point I have to admit my lack of early cj knowledge. I titled this post bad alternator and the whole time I have a generator...duh.
Ok so I hear there is something called "reversed polorism" ( I work with people that have this I think) but anyway as I understand it you have to disconnect the positive terminal and somehow spark the generator back to charging the battery. When I pulled the battery out a couple weeks ago and then put it back in, it caused the generator to reverse and started draining my battery instead of charging it.
I have my battery charging today. Once I am back to a full charge what is the next step in reversing this generator?
Thanks

 

Doc Vern has written some stuff up on polarizing a generator:

http://www.vernco.com/sparks/id569.htm

 

Just the info I needed, thanks!