Alternator or battery?

[turbojimmy]

Hi all,

The past couple 'o mornings the battery in my '99 Century has been dead. I *think* the battery is fairly new, I but I don't know for sure. Yesterday, I charged it for a few hours. Drove it around all day and it was fine. This morning it's dead again.

Alternator is charging. I jumped it this morning and drove 20 miles to work. Shut it off once I got here, and it restarted fine. I unhooked the battery just in case it's the alternator.

Can a bad alternator drain the battery? I know it happens to Fords. There's no obvious drains and the car is smart enough to shut off any lights that might be left on (interior, trunk, headlights, etc.).

I hate to buy an alternator and find I need a battery, too. Or vise versa.

I have a DVOM, but all I checked so far was the battery voltage key off, engine off. It's fine.

Thanks,
Jim

 

[IrvJr]

Mine was doing this as well. It turned out to be the battery which was about a year old. It was reading 12.5 volts even at WOT. I took it to a parts store and they checked it out, after i took it out of the car, and it tested bad on their in store tester. But tested good on the portable unit. I belive if the car runs fine and doesnt die the alternator is charging, but that doesnt mean the diode isnt bad and draining the battery.

Scott

 

[Jack Evers]

Moved to Tech Section

Hope you don't mind, but I'm going to move this thread from the Lounge to Buick Tech. Good information and should reach broader technical group over there.

 

[turbojimmy]

Re: Moved to Tech Section

Originally posted by Jack Evers
Hope you don't mind, but I'm going to move this thread from the Lounge to Buick Tech. Good information and should reach broader technical group over there.

Fine with me. Just non-TR, that's all.

Jim

 

[gofstbuick]

try load testing the battery first.

 

[turbojimmy]

Originally posted by gofstbuick
try load testing the battery first.

I'm thinking it's the battery. I went out at lunch time and hooked the battery back up. It's stone dead again - after having been fine this morning when I disconnected it.

Thanks for the replies.

Jim

 

[G-boz]

A way of checking the alternator is, start the car, when the cars running, unhook the positive cable, If the car dies, Its the alternator. and yes a bad alternator may drain the battery,I had a chevy with that problem!

 

[gofstbuick]

IMHO, not too good of an idea on computer controlled engines.

 

[turbojimmy]

So far so good with the new battery. I had my uncle ship me an alternator, too, because this one is making noise (sounds like brushes). He gets them out of wrecks, so they're not new but since most are fairly new factory pieces they might be better than rebuilt ones.

Anyhow, looks like the battery fixed it. It's always something.

Jim