Dead battery - Is the alternator bad?

[3point2]

Hi-

I was driving one day on the freeway and the radio shut off and I couldn't get it to turn back on. However, the car was running fine. I pulled the car into my garage that day, armed the car, and came back 5 days later to find that my battery was completely dead. I took the battery to Autozone to have it checked out and they said it is fine.

My next thought was the alternator needs to be replaced. But I was thinking that since the battery completely drained after sitting in the garage for 5 days, it may be something else that's draining the battery. Or is this normal with a bad alternator? Could it be the voltage regulator or something else?

Thoughts?

Thanks for any help!

-Leo

[thom4782]

You might be on the right track. If it is the alternator, then your left driving off the battery. It will drain and eventually die. And that might explain your dead battery. Only way to really tell is to get the car started and measure the alternators output. I know I'm stating the oblivious but that's where I'd start.

[tonycarreon]

did the battery light come on? how far was the drive from the dead radio to home?

when my alternator died, the battery light came on and the car died after about 15 miles.

[Ian c]

You need to get the battery charged and back on , then check voltage .
12vdc on the battery 13.8vdc running .
Then disconnect the earth and put your multimeter on miliamps and see what your drain is with everything turned off .

[3point2]

Thanks for the replies.

No battery light came on. It drove fine on the way home the last time except the radio died. And then when I came home a few days after the car was parked tor restart it, the battery was completely dead. Can the battery completely drain that fast on its own even when the car is turned off?

I'll pick up a voltmeter and check the voltage tomorrow.

What is the earth connection? Where is it located?

Thanks again!

[cas951]

Originally Posted by 3point2

Thanks for the replies.

No battery light came on. It drove fine on the way home the last time except the radio died. And then when I came home a few days after the car was parked tor restart it, the battery was completely dead. Can the battery completely drain that fast on its own even when the car is turned off?

I'll pick up a voltmeter and check the voltage tomorrow.

What is the earth connection? Where is it located?

Thanks again!

He meant Ground cable. The black cable at the battery terminal. If you have a volt meter connect your wires in series from the neg cable to the negative battery terminal. If there is any voltage drain it will show on your meter. You can disconnect your fuse 1 x 1 till you no longer see any voltage reading with the voltmeter.

I'd start with the radio fuse first.

[dghii]

If your battery and cables are ok, you most likely have a bad voltage regular. The regulator is on the back of your alternator and is a generic part which costs less than $50.

My car did the exact same thing back in mid May. It finally through an overvoltage code. This repair is not too difficult but will test your patients a bit. Lots of good write ups available.

[Ian c]

Originally Posted by 3point2

Thanks for the replies.

No battery light came on. It drove fine on the way home the last time except the radio died. And then when I came home a few days after the car was parked tor restart it, the battery was completely dead. Can the battery completely drain that fast on its own even when the car is turned off?

I'll pick up a voltmeter and check the voltage tomorrow.

What is the earth connection? Where is it located?

Thanks again!

Originally Posted by cas951

He meant Ground cable. The black cable at the battery terminal. If you have a volt meter connect your wires in series from the neg cable to the negative battery terminal. If there is any voltage drain it will show on your meter. You can disconnect your fuse 1 x 1 till you no longer see any voltage reading with the voltmeter.

I'd start with the radio fuse first.

Oops !!!
My English slipped out after a few beers
Yeah , earth is ground .
You will need a multimeter with milliamps to do the fuse check easily but you can pull all suspect fuses , and any non critical fuses , and work that way .
It will just take longer .

If you are going to buy a multimeter , get one with voltDC , voltAC , continuity/ohms , and amps/miliamps . This will cover most of your uses around the home and car , and once you have one you will find uses for it

An analog is accurate , but I suggest you get a digital .
Have a look on transcat for a fluke , and you can probably pick up a bargain on Craigslist or eBay .

[Ian c]

Just had a quick look on your local CL ...
This would be more than ideal for 75 bucks if it has leads etc .

fluke multimeter

Or this one for 100 .

http://sfbay.craigslist.org/pen/tls/4043200302.html

This one is older , but cheaper . At 60 bucks

http://sfbay.craigslist.org/sfc/tls/4047183659.html

[3point2]

Helpful posts! Thanks!

I just checked voltage with the car off and it's at 12.2V. With the car on, it's 14.3V. So does that mean the alternator is good?

I'm starting to suspect that something is draining the battery from somewhere. When I was driving the car the last time, the radio went out. Now with the battery charged up it works fine. When the car sat for a few days, the battery was completely dead.

Any other thoughts?

If it was the voltage regulator, the voltage would be showing up all over the place on the multimeter with the car on, right? It holds a steady 14.2-14.3V with the car on.

[Ian c]

It is within range but how long did you leave it running for ?
it could drop off after a while so put your lights on and keep it ticking over for a while .
what meter did you get.
This type of scenario is why i use flukes with min/max and logging etc.

next you need to disconnect the ground and put your meter across battery- and disconnected - clamp wthen close everything .
This willtell you what your drain is running at .

[3point2]

Ok. I just restarted the car and the voltage is now reading 13.9V. Voltage is going down slowly even with the car running.

Sorry Ian. Don't quite understand. Do I disconnect the ground while the car is running and then check voltage?

[Ian c]

Sounds like the regulator and or alternator is going .
It should read steady with a small load on it like lights on .
Everything else turned off , and don't forget the hvac controls ...

The drain check is with everything off to take an amp reading of what you lose from the battery with the car turned off . (Ie: parked over night)

[3point2]

I left the car running for 15 minutes and with the headlights on. Voltage got to as low as 13.48V. Then I turned off the car and the battery is at 12.5V which is slightly higher than earlier i checked.

Ehh electrical gremlins are the worst.

[Ian c]

Them figures are t the end of the world .
It dropped but still was high enough to produce a charge for the battery .

Did you get a meter with dc amps ?

[3point2]

Here's a pic of my meter.



Shall I start removing the firewall cover and get started on removing the alternator? Lol

[Ian c]

I can't see properly as I'm in the car on my cell , but it looks like dCA ?
If it is , that is dc amps . Perfect.

Disconnect the ground as described earlier and take a reading .
Make notes and remove fuses one at a time and note what it goes down to .

I forgot to add earlier . Your meter co. e toons must be good .. If using probe pins scrape first and if using clips lamp them on the. Use the grips to clean the surface .

I will be home in an hour so will call back on here but hopeful someone else will rey a out your drain readings if you're having trouble

[3point2]

It's DCA on the left side of the meter.

So I removed the negative cable from the battery.

What setting do I use on thE meter? 200milliamps?

Then with the car off I take a reading at the battery and pull one fuse at a time in the drivers side footwell?

Do I replace the fuse after each reading?

[Ian c]

Yeah
That's exactly how to do it .
One at a time and replace after noting the reading .
You should be reading around 20-25 milliamps so if you have a smaller range on your meter it will be fine .
The idea is to find how many mAs your car drains with all doors shut and locked (simulating a parked scenario)
And if it is high enough to flatten your battery you pull one fuse at a time to find out which circuit has a fault causing excessive drain

[3point2]

Thanks for your help.

Before I go check fuses, from what I've seen so far, could the alternator still be good?

Thanks again,
-leo