Major Battery Drain


May 12, 2008
Had my battery and alternator checked at Advanced Auto yesterday because as others have had a loss of volts under boost. They said had a drain on the battery, showing 10.8 volts (that seems way out of line-is it even possible?) when placing the meter between the negitive post and the disconnected cable.

So I pulled the fuses and it did not show any drop. All that has happened since she ran good was:

1. New MAF sensor (car was running rough ever since I got it), new MAF eliminated that issus.
2. Pull the dash and remove the stock alarm system and graphite the speedo cable.
3. Put a field fix harness on, as we had no volt light after dash replacement, probably didn't get the connector from hell aligned correctly.

Where else can I look? After market alarm gone bad?

You started right but you forgot to unplug things as well. Do you have a test light? If you do take the neg cable off and hook up the light between the cable and the batt. Then unplug each item like the alt plug and any other item that might suck the batt dry. Good luck.
Meter hookup was correct for measuring batt drain, but the meter should have been set up to read amps, or milliamps instead of volts.

Check the amperage reading to see if you really have a draw on the battery.
Reading should be in the milliamp range if you're ok.
should be 50mA or less
make sure all accy are off and key is out or youll blow fuse in meter
undo neg batt cable and have on meter lead on the cable end the other on the neg batt post...good luck!
Do you still have the factory AM/FM radio? The clock circuit has been known to cause a drain on the batt if one of the transistors goes bad.

Does your car have a Volt booster? I have had two go bad caused Batt drain. I would check the connector that plugs into the alternator make sure it looks A-1 "no crud, bent prongs etc... hope this helps
1. Yes I have a test light.
2. With regard to m, meter has m setting under the volt side and under the amp side which range for 20m to 2000m. Does it matter which side I use and would the 200m be the best setting? Does the fact I used the volts to do the fuse check mean I need to pull the fuses again? Would think not, but thinking sometimes gets me in trouble.
3. With regards to 50mA or less, if it is more than 50 then we have issues?
4. Have factory radio, but no clock light with key off, can there be other issues too? Would I have seen results of such an issue when I pulled the fuse for it?
5. How do I tell if there is a volt booster? I ask because the guy before me put on a field fix, which I didn't know until the new one I ordered showed up and the two looked exactly alike. Did not have a clue what a stock harness looked like.
You start at the highest Amp. scale with Amp. readings.

See if the meter has another port on it for high current tests such as 5A or 10A or 20A scale. Usually a separate red probe input on most meters for that scale.

If you use the 2000ma scale be careful as that's only a 2A reading and you could peg the meter easily with a draw on it.

If all is normal that scale won't register much and you can work your way down in scales so the meter moves.

I would say more than 50ma could be issues, get an accurate reading and report back.

Many "issues" however are aftermarket stuff hooked up a bit wrong.
It has a 10 A input jack, so I guess I should use that? Then what do I look for on the read out?
Assuming a digital meter you hook the red into the 10A spot and leave the black where it is.

Take the reading with all doors closed and the hood lamp bulb pulled out of the socket and trunk closed no accessories or keys on.

Report back the reading from that scale.

If it's like 005, or some low number go to the next smallest scale which is probably the 2000ma scale and take a reading and report that.

Report what scale you are on when you report the numbers.

A negative reading on a digital meter means the cables are backwards and it is showing current in the opposite direction, no biggy for this test.

If it's an analog meter with needle it will peg backwards so reverse the leads, always touch tap quickly the connection with an analog meter to make sure it goes in the right direction, first off, otherwise you can damage it pegging it against the 0 stop.
New news. I have been checking the battery since fully recharged it, it from 12.8 to 10.8 in two hours. I pulled the battery and took it back, they rechecked it and said it was bad. They gave me a new one and I drove it and the volt meter and the Scanmaster read between 14 & 13.8. Under boost it dropped to 13.6. Not under boost and stopped at lights it would go 13.8 down to 13.4 and then bounce back up. Had a slight hesitation on the Turbo when punching it. Then seemed to get better, maybe the computer finally reset itself. It is rush hour here and no place to kick it again, so will wait until tomorrow. I am taking a reading of the battery and then check it tomorrow and see what is up then. Will report back then.

My scanmaster alternates between volts and temp. a lot when driving. :eek: :biggrin:

Don't beat on the car until you figure out the electrical issues fully.

Volt readings seem to be in the normal range for cool weather driving with a good battery now. :smile:

Keep an eye on them.
Checked the battery volts @ 4:30 PM yesterday and it read 12.8, checked again at 4:30 AM today and it was 12.68. Is that small drop acceptable? I bought a Ground Stretcher from Caspers, I am wondering if I should install it or forget it now. Everytime you seem to do one thing something else. I have also seen pros and cons on volt booster, any thoughts on that?

No, should I try with it running? When I checked it before the old this way it would drop from 12.7 to 10.6 in 3 hours. I was attempting to see if I had a drain.

If the alternator and battery is good, you should be reading around 14 volts when the car is first started, then it will drop a little lower after the car has run some.
I know that is how it read yeaterday, both times I took it out, this reading was from the Scanmaster. I will check it again when I go out. This is the second battery I have put in about 6 months from Advanced Auto, both were defective. They said it was there best battery, except for the Optima. They only have a 26 month warranty. I am thinking I might spring for a better one and keep this one for a spare. Any recomendations?

Me personally, I've always used Sears (gold) diehard , never had a problem with them, but there are alot of good batterys out there.
Meter hookup was correct for measuring batt drain, but the meter should have been set up to read amps, or milliamps instead of volts.

Check the amperage reading to see if you really have a draw on the battery.
Reading should be in the milliamp range if you're ok.

Yeah that should be the right thing to be done when measuring the battery....