Need help figuring out what accessory is drawing from the battery.

[dirtyone55]

Ok, long story short, I am trying to help a buddy figure out a problem on his dad's jeep. The problem is that the battery is running dead while the car is turned off. The battery is brand new, and has been tested twice and charged twice just to make sure that is not the problem. the alternator has also been tested, and is also working properly. So that leads me to belive that some accessory is still drawing while the vehicle is off. I know there is a way that you can use a multimeter to check and see if something is drawing while the ignition is turned off, but I can't remember what setting the multimeter needs to be set to or where to put the testing probes. I would say that once the multimeter is set up, I could just go through the fuse box and pull fuses individually and see when the draw decreases and be able to kind of pin point where the problem is coming from so I do not have to tear things apart that are not the problem if I can eliminate some of the guessing. I do know that there is always going to be a draw from the battery no matter what for the computer and the radio memories to store the clock and preset settings and such.

If anybody has any information, or any other ideas on how to pinpoint the problem on hand, I would greatly appreciate it. Also, if testing to see if there is a draw, what is the safe range that the multimeter should read to account for the radio and computer?

Thanks.

[chad393na]

Set your meter to the ammeter setting and connect it between the neg post and the neg cable end. Most meters can take a max of 10 amps, so if it's higher, you may have to replace the meter's fuse. If this happens, use a testlight in place of the meter. It's not as comprehensive, but will work in a pinch. Start pulling fuses until the draw disappears. Also try disconnecting the alternator, it can short internally and cause a drain. Good luck!

[dirtyone55]

Thanks. I do appreciate it.

[PaulFiveOh]

If you have something drawing 10amp/hours at rest....your batt would last for about 15 minutes.

Also, I think it is easier to put the ammeter on the system you are testing. That way you don't have to worry about stray amperage on the neg side giving you a 'red herring' effect. So for instance if you can stick your probes inline with a fuse then that is the best way to go, IMO.

[dirtyone55]

If you have something drawing 10amp/hours at rest....your batt would last for about 15 minutes.

Also, I think it is easier to put the ammeter on the system you are testing. That way you don't have to worry about stray amperage on the neg side giving you a 'red herring' effect. So for instance if you can stick your probes inline with a fuse then that is the best way to go, IMO.

If I were to do that, then what all fuses will there be a slight draw on besides the radio fuse? Just so I am not thrown off by a draw that is supposed to be there.

Thanks.

[mustang8998]

Does it have vanity lights, in the sun visors?

That happened to me once and it drove me nuts, trying to figure it out!

[dirtyone55]

I dont know, I will check though. I am just trying to narrow the possibilities down a bit before ripping everything apart.

Thanks.