CliffH

1991 5.0. After 5 days of not being started, I fired her up no problem. As I drove off it started to loose rpm's and the battery light came on. It eventually died while idling. Started back up and finished the two mile drive no problem. From Friday to Monday it sat. Today (Monday) it did not start. It will start with a jump but dies after a minute. I had cleaned the battery posts off two weeks ago. Just replaced the terminals. Autozone said the battery tested with a bad cell. I don't know how old the battery is. Is that all the problem may be? Or should I have the alternator tested? Thanks for reading this novel.

94FordI6

If everything is clean and tight put a volt meter on the battery, with the truck running it should be around 14.4 volts much lower then its not charging.

dirtcrew51m

Check for voltage at the battery with the truck running, if it has 14v+ the alt is good, if there is less than 13v the alternator is bad, and if there is 11v or less the battery is bad.

Crownman

If the battery tested with a bad cell then the battery is bad. And, with it running you should be able to disconnect both battery cables and it should still run fine off the alternator, if it doesn't then the alt is bad. There's a good chance that the bad battery caused the alt to go out also, seen it many times.

Just call me Sean

iTrader: (1)

You can't do that anymore, don't test the alternator by disconnecting the cables it can fry it.

Sounds like both to me. Truck should run with a battery with a bad cell.

CliffH

Replaced the battery. I'll check voltage when I return the core. This was not a foreseen issue, but she deserved a new battery after 22 years of service. An alternator won't cost much more if it becomes necessary. Thanks for all the help.

CliffH

Check engine light came on before I made it the 2.5 miles to work.

Crownman

I've done it a million times. It won't hurt anything. I jump started a car with no battery and made an hour drive, it was fine. The vehicle runs off the alternator anyway and just uses the battery to get it started.

Forge-World-FORD

Just waiting for Sean to come back and say something. These situations always entertain me.

Also...just putting this here..

http://www.troubleshooters.com/dont_...ct_battery.htm

And this

http://www.batteriesnorthwest.com/batteryschool.cfm

Just call me Sean

iTrader: (1)

That pretty much covers it. Only people that don't know what they're doing disconnect the battery with the engine running. It's not a lawnmower.