Question How Do I Find An Electrical Drain?????

[TheGryme]

Hi....
I have a Black, V6, 4Runner with Downey / Rancho suspension F&R, 3 inch sus lift, 1 inch body lift, SAW T-Barz, 4:88's, ARB (rear), 32X12.50 BS Dualers on AR 8X15 Wheelz, Power Slots and Pads, Downey headers, MagnaFlo Muff, K&N FIPK, Ported heads, 1 piece stainless valves....
My problem is the truck recently started having a dead battery if it sits all week long....which is very usual for this rig. I jump it and it starts just fine. If I dis-connect the battery.....let it sit a week or two....then reconnect....It starts just fine....So I'm guessing I have a electrical drain somewhere....{or Gremlins.}
I pulled the negative terminal off yesterday on put a 12 volt cirquit tester light in between the ground cable and the batt post. The test light was on indicating that something is using battery power...we pulled every fuse and relay we could find and still the light glowed....CRAP . I was hoping a circuit would kill the light and then I'd have a place to start.....
Does anyone here have any suggestions on how to find a electrical drain?
Any help will be appreciated!
O yeah......the battery is almost new...belts are good....and there are no lights on inside the truck when the doors are closed (I looked!).etc.

[Eddie]

You need to use a multimeter,not a test light. The light itself was causing the power draw,that's why it lit up even with all the fuses removed.

This is a good how-to article Battery Drain Parasitic Draw Testing

[TheGryme]

Thanks.....I'll try that next weekend!

[duffyatkinson]

I'd first check all power-related accessories, i.e. aftermarket stereos (especially amps and crossover connections), CB radios, winches, inverters, et al that are installed. They are notorious for creating large parasitic draws as well as shorts. Disconnect each in turn and retest.

Next, get a fused ohmeter to test for a systemic short and determine baseline power draw.

Frayed wiring is quite often a culprit when unacceptable battery drains occur. Unfortunately, it can wickedly difficult to find the spot that is causing the trouble.

I hope you get to the bottom of it without too much hassle.

[Mr. Creosote]

The problem with rail shorts (or partial shorts) is the sheer number of potential culprits, since everything is hooked to the rails. Ironically hard shorts are easier to find because a low range ohmmeter can often lead the way, but a softer short doesn't give up too many clues. I would also look at the alternator as a fair first guess. I know in some Chevs the diodes would break down and cause some parasitic drain.

[Hi Volt]

With all the fuses pulled, a glowing test light will still indicate a live circuit or fault. An ammeter in place will give you a magnitude of the draw and can rule out some possibilties more easily.

I am assuming that you pulled all the small fuses but did not disconnect the large alternator fuse ? This one usually has the wires bolted to the bottom and can be 100 to 120 Amp size and is a pain to remove ( earlier vehicles used a fusible link wire ). A problem area can be a bad diode ( shorted ) in the alternator. This will cause a drain during engine off conditions, however the alternator will still charge during running conditions although the output is not as high as normal. A lab scope would pickup the bad waveform, however we will keep it more simple to test.

Short of removing the alternator fuse ( large one, usually 100-120A, not the low current field fuse 10-15 A) the simplest way to check this is to disconnect the large gauge output wire from the back of the alternator and see if the drain goes away. However you must keep in mind that this wire will have live battery power on it so don't let it short out. You can either wait a week this way and see what happens, or install the test light, but preferably an ammeter if you have one ( set to 20A range to begin with ) in series between the removed battery cable and open battery post. Again with all the fuses pulled as before note the drain, now disconnect the alternator wire and see if the drain goes away. If so it is alternator re-build or replacement time, otherwise a value from an ammeter would help determine the type of drain.

One final note is to remember is that it is common to have 2 or 3 fuse panels today, one under the hood and one or two in the kick panels or under dash. Checking your owner's manual will show them all (just to make sure you are getting all of them).

O.K. a second final note, do you have any amps or anything directly connected to the battery ? If so make sure you catch these fuses as well or disconnect them from the battery to see the effect on the draw.

[SE2000]

The ammeter is your best bet, along with a multimeter to find the cause. Aftermarket stereos are big culprits. A leaky cap will drain you.
A battery cutoff switch may be the cheap and dirty solution if not killing your battery is your only concern.
I'd go for the fix but I know electrical systems, most people don't. And you have to think about part costs