Battery still won't hold a charge...

[AMiller320]

Hello --

I'm having continued electrical issues with the Grand Wagoneer (1988). It starts with a jumps start, but doesn't hold the charge -- it dies pretty quickly. I figured new alternator, right? Well, I took off the alternator, and saw that the wire plug had rusted off on one side. So, I replaced the alternator and the plug. I hooked it all back up tonight, and the same thing happened. I jump started it, then it ran for about 90 seconds then quit.

The battery is less than a year old, so I think that it's okay. Maybe I'm wrong -- is there an easy way to test it? Is there anything else I should check, or is it time to start poking around with the voltmeter? Not that I know what I'm looking for...

Thanks for your help.
Andy>>

[porkchop]

That sounds like a bad alt to me. Did you test the new one before you left the store? When I bought mine I had them test it first. The guy at the counter looked at me like I was crazy but I insisted. It turned out that the new one had a bad diode. Charge the battery over night and see how long it will run after a good charge. Did you check the voltage coming off the alt with a voltmeter? Also have you looked at the water level in the batt? If it is low fill it up with distilled water and then drop an asprin in each cell, my grand pa taught me that many years ago. It supoosedly raises the acid level. Who am I to argue with my grand pa? I have done it ever since.

Just a few things to start with.

[shadowfax101]

If your battery is two low you could kill the alternator, or so claima that little tag that comes on the alternator. Plug a volt meter up to your battery and see how many volts you have before you start to jumo it off and crank it. I would also try to take the alternator back and get it checked...good luck. One more thing, what is the amp reading from the dash. if you jumped it off it should go way up for a while until your battery is charged. That can give you some hints to if your alternator is putting out..

[bchesley]

One thing to add. If you put a new alternator on and know that the battery is good how can you be sure that the charge is actually making it to the system. Once you jump it off check the voltage at the battery, it should be elevated because of the current coming from the alternator. Next try running a wire from the out put side of the alternator straight to the battery and see how long it will run. If it continues to run that the problem is in the wiring.

[coolram]

shadowfox is right,check battery voltage before you jumpstart,leave your meter leads on the battery terminals after you start.Static battery voltage should be be 11 to 12.5 and shouldn't drop below 10 when cranking.Wen running voltage should be around 14 if charging.Battery could have a loose plate discharging it.And have the alt checked too.

[AMiller320]

Thanks for everything so far! Here's my responses:

- I didn't have the alternator tested when I left the store (NAPA). It took me an hour (!!!) to get the right one, and I didn't feel like hanging around any longer.

- The amp reading on the dash gauge is good right when I first start it, but then it drops like a rock.

- I have not tested the output from the alternator. What wire to I test, and what should the reading be? There's a plug on the side of the alternator with two wires, and a single wire off of the back that's attached to a threaded post.

- I've never filled a battery before, do I just pop the top off and fill it up?

- Tonight I'm going to charge up the battery all the way, then I'll test it.

- Taking it in to get it tested is last on my list, mostly because I'm lazy and don't want to take it off again smile.gif Really, I only have an hour or so each night to work on it so my time is pretty limited.

Thanks again!

Andy>>

[River Beast]

This is an old shade-tree method of isolating a problem....

start it up... then diconnect the positive lead from the battery.... if the alt is good she'll stay running soley on alt pwr...

If it dies... one of two thing could be wrong....
1. bad alternator OBVIOUSLY :D

2. an open circuit completing the charging cicuit.

Have the battery completely charged by a shop.... then load test on the bench with a heavy load to see if it withstands the load and holds a charge....holding it's amperage and volts.... and battery can maintain it's voltage and have no amperage.... I've had one of those.

If the battery checks good, and the rig dies... have the alt check on the bench.

IF both check out good, you most likely have an open circuit....

OR.... the voltage regulator is gone... not allowing the charge to go to the battery

Use distilled water in the battery... ;)

[ December 18, 2001: Message edited by: River Beast ]

[la mula pescadora]

This is an old shade-tree method of isolating a problem....
start it up... then diconnect the positive lead from the battery.... if the alt is good she'll stay running soley on alt pwr.......

thisis a good test but it is done in just the cars with out a computer because you can create high voltage spikes and burn it

i whould recomend to check the battery or use a loaner from another car sometimes a battery is hable to read 12 volts but once u crank it or apply load on it this voltage goes down

[AMiller320]

Update:

I charged the battery fully (hopefully my neighbor doesn't notice his missing batter charger), and measured it with the voltmeter. It read around 13. Cool.

Started the truck (in all of it's glorious leaky-exhaust thunder) and it measured around 11.5. No good.

Killed the engine, and again measure the connection from the alternator output back to the battery. It measures (ohms) fine. Also checked from the batter to the alternator. Again -- fine.

That points to a faulty alternator, right? I'll take it out tomorrow and bring it in to Napa and have 'em test it, and replace it possibly. If the alternator tests out okay, what else could it be?

Man, I need to get this done soon. The snow starts flying here this weekend, and it's about to get wicked cold around here. I hope Santa brings me a garage heater.

[reddog]

I do not know about your local Napa but alot of the chain stores can test the alt in the car - call them up and ask, it may save you the hassle of removing it. If it is bad you could swap it right there in the parking lot!

Kerry

[la mula pescadora]

take off your volage regulator and take it as well to have it check well that's if you hav an external one

[AMiller320]

Well, that's how I'd like to do it, but the "local" Napa is like 15 miles away. I don't think the Waggy is gonna make it there in one piece without the alternator!

Taking it off isn't a huge deal, just kind of a PITA when it's cold and time is limited.

[AMiller320]

WOOOOO HOOOOOOOOOO!!!!!!

The Wagoneer RUNS! Excellent! Turns out there was a broken brush in the new alternator. God bless warranties. Got a replacement (had it tested at the store this time) and hooked it up. We're good to go now!

And just in time... got a few inches of snow. I think I LOVE four wheel drive.

smile.gif smile.gif smile.gif

[porkchop]

Always helps to have it tested before you leave the store. :D :D

[Va-Rob]

If you want to ensure the alt. is bad disconect the positive lead while it is running. You should never do that.

Rob