Last week the battery in my '94 Econoline suddenly died. I replaced it with a new one and now that one suddenly died. I assume there is a short somewhere that is draining the battery. Any suggestions on the most likely place to find the problem?

 

I had the same thing happen twice in the last month. The first time I assumed it was caused by my corroded battery posts. The second time, I did everything mentioned in the "Wal-Mart Batteries" thread - and found my own advice to be the cure.

My amp gauge was NOT showing ANY charge after a start. Normally you will see the amp gauge needle rise higher than usual after a start, then kick down to normal as the alternator recharges the battery. I had a bad alternator.

Read the recent WM Battery thread - I believe most causes and cures were discussed there.

Broncr

 

its the alternator, or check the alternator fuse

 

A good way to ceck out your charging system is to hook a voltmeter (multimeter) to the battery when the engine is running. If you have less than or equal to 12 volts across the battery, then your alternator may be the culprit. Also, make sure you have a good ground too.

Dan

 

You should have around 13.5 volts when the engine is running. At 12 volts when running something is wrong. I believe anything less than 13 volts isn't real good.

Also make sure your belts are good and tight. An alternator belt should always be tighter than you think it should be. They can slip under a load on the alternator. A loose or slipping belt will give you the condition where the more you drive it the more dead the battery gets, the opposite of what you might think should be going on. One night of driving with the lights and heater is enough to kill it.

I learned all this many years ago from a guy with an auto electric shop. I wasn't exactly green at the time but couldn't figure out why my battery kept going dead when everything checked out fine. "Loose belts," he says, and tightened them up more than I ever had done. They didn't seem loose to me when I went in. I went away a little embarrassed by such a simple thing and still a little non-believing. But the problem went away and stayed away. I think of that every time I adjust an alternator belt to this day. "There - tight enough," I say. And then I tighten it a little more.

 

I use a voltmeter hooked to a connector that plugs into the cigarette lighter.
Measure the battery voltage with the engine off then turn the engine on and recheck the voltage. Should be about what RMT says. Then put on all ellectrical loads, while driving, AC, cruise control, radio, Blower on High, Headlights on high beams. If the laternator is good it should carry all the loads and still be at 13.5 volts or a little more.

 

My alternator went out after 2 years of showing a "lower" state of charge on the amp gauge when I turned the lights on. Buy a new alternator don't mess with rebuilts......save the headaches. Now my amp gauge is rock steady with everything on.

 

A fully charged battery should read 12.6 volts with no load. When charging, 13.5 to 14.5 is about right. If you are getting these kind of readings, then alternator is charging OK. There are very few if any loads on a battery with everything off. If alternator has a shorted diode there will be a definite spark between main alternator post and lead with engine off.