Bad Battery?

[tyb323]

Hey gang.
So I'm at one of Colonel Sander's fine establishments and glance down and my voltmeter is reading steady a few milimiters above the first yellow slash. Now for the past several days, everytime I come to a stoplight with all the accessories on, it was reading a bit below 13 at stoplights, something I don't remember it doing before. The other day it chuffed a bit getting started. And on the drive back from KFC, the volt meter would NOT get back up to 13. It would go up a bit, but drop back down at stoplights. So, am I right in assuming my battery (5 years oldish) has taken a nose dive and the alternator is the only thing keeping my car alive?

[TTait]

In theory the battery is only there to get the car started, and the alternator is supplying all of the power needed to run the car, plus a bit to recharge the battery from the last start.

The primary exception is if you have a heavy load while at idle, the AC and headlights and probably the stereo on. Depending on your alternator it may not do well at idle - especially if it is a high amperage unit. The irony there is that the high output alternator provides more juice when at running speed, but it may provide little or none sitting at a red light. Beware high output alternators, no need to get a huge one unless you are running a mega stereo or other added load. The unit currently sold by Houston is an excellent balance of available power and good power at idle.

So, back to your problem - it could be the battery - it is 5 years old - but even if the battery tests bad, that may not be the whole story. A battery will die faster if the rest of the charging system is not up to snuff.

Clean and check the connections at the battery cable hook ups. Also go under the car and clean up the connections at the other end of the + cable and the ground. Clean all the contacts at the alternator and clean up all the grounds on the car (search this site for good lists).

Turn your key one click till the idiot lights come on, and make sure the battery light comes on. If that bulb is burned out the alternator can't charge the battery properly. Replace the bulb first if it does not come on.

Then put the battery on charge overnight, and see how you do - if you still have problems take to to the auto parts shop and have them test it - a proper test usually takes 20 minutes or more.

At this point use a meter to check the voltage across the battery terminals should be about 12.5 volts with the car up, and go up to 14.25 or so when the car is running. If not, you may have to have your alternator checked too.

Let us know what you find.

[Ron]

Could be the battery or alternator from the info. At 5 years old it's probably time. Anyway, the voltage on a battery that starts the car on it's own after sitting all night will usually go to 13V+ pretty quick if you don't load it down at idle. If you think all of your connections including grounds are good to go, I'd take it for a free check. If it showed good and I had the cash, I'd get a new one because of it's age -- But be prepared that the alternator isn't keeping it up in the first place (take it with you to get a free check too).

Note: If an aftermarket "High Amp/High Output" alternator is not charging at idle on a D with the full factory equipped load (and more), it needs a smaller pulley to compensate for the relatively huge difference in the drive pulley circumference the replacement unit was intended for. (There are pics and the simple math on it here some where...)

[Michael]

You should start with a good battery first fbefore checking anything else, even grounds. Have yours load tested, but at 5 years old, I would just go ahead and replace it. Once the battery is known to be good and a problem persists, then you can check grounds, alternate, etc.

[Bitsyncmaster]

Your battery may have a shorted cell. Since yours is 5 years old, I would just replace it. If that does not fix the problem than most likely your alternator or connections.

[tyb323]

What is this "woo" sound I'm hearing in the engine bay?

[Ron]

What is this "woo" sound I'm hearing in the engine bay?

"How's that go again?" :p

Does the engine turn over while you hear it?( If not, it's probably a bad starter drive...)

I think we need a vid for this one.

[tyb323]

It starts up fine. My voltmeter is still hanging around 10-11. I''ll see if i can make a quick video

[tyb323]

http://www.youtube.com/watch?v=87h10FPrVek&list=UUbaQZOfcA4X3whRkAAdsy8A&index=1&feature=plpp_video

So here it is. It would be a pretty sweet sound IF it weren't something bad.

[Ron]

It does sound odd! Could be a internally shorted alternator (they "groan" instead of "whine" or "hum").
The vid is very dark on my monitor but I didn't see the BATT light flash or come on when you first turned the key...maybe to fast or it was off screen?

Stab in the dark: If this noise is new too, drop the alternator belt and see if it goes away.

[tyb323]

The battery light works, it was covered up by the wheel in this video.

[Ron]

And w/o a belt on the alternator? ...Don't you have one of those new belt adusters everyone was trying?

ooop...steak is done I'll be thinking about you pulling a belt while eating it ;-)

[tyb323]

I unfortunately do not, and as I am traveling out of state, I don't have a prybar with me to retension it properly =(

[Ron]

I unfortunately do not, and as I am traveling out of state, I don't have a prybar with me to retension it properly =(
You could disconnect all of the alternator wires, if you have a way to keep those on the main terminal together so everything else gets power...maybe a nut and bolt or vice grips...just keep from shorting things out...