Tracking down that battery drain- light bulb test??

[Bundy]

Hi all-

my battery has a drain, trying to chase it down. i was told i could either use a multimete or a light bulb to see if there is any drain on the battery by putting the light or MM in between and seeing if there is any measurable voltage- or at least i think that is what i am supposed to do.

so i am using the multimeter, have it set to VDC (20). do i put a MM terminal on the power cable to the onboarder welder and the other to the battery positive terminal? that doesn't seem right?

Help please!?:?

 

[Viperwolf1]

so i am using the multimeter, have it set to VDC (20). do i put a MM terminal on the power cable to the onboarder welder and the other to the battery positive terminal? that doesn't seem right?

Help please!?:?

That's correct. Positive lead to the battery terminal. Ideally you should see 0V. If you see battery voltage then you have something turned on or there's a drain.

 

[904Bronco]

Simplified version:

Disconnect positive battery cable from battery
put VOM or 12v test light in between batt post and positive cable (and or anything else that is attached to the battery). Does the test light light up or is there measurable voltage?

If there is light or voltage, start removing fuses to see if any of the circuits are causing a draw. (pull fuse and if light goes off/voltage goes to 0 you are getting close) Now what is on that circuit and check each item. Same goes for accessories connected to the battery and the alternator.

It will take some time...

 

[Steve83]

Don't use a light - depending on exactly which one you choose, you may see light with a normal draw, or NOT see light with a heavy draw. But you should always see 12V, so don't use a voltmeter.

Use an ammeter. Anything above 50mA is excessive, but most vehicles draw less than 20mA with everything off. If you have a draw higher than your meter shows, you'll blow the meter's internal fuse, and it'll show 0.000 .

 

[roundhouse]

You can use a light and start pulling fuses one at a time to figure out which circuit is drawing.

But on EBs there isnt that much it can be, radio or dome lights, thats about it, unless the alternator is draining it off somehow.

 

[av bronco]

If you have a cd/amfm stereo it will show with a voltmeter or test light, it has a memory constant hot, it will be very little but it will still show.

 

[Bundy]

so i started testing everything hooked up to the battery- i used the multimeter on the VDC setting and the line going to the first fusebox was reading 11.3- when i pulled the bottom fuse (in pic) it went to .0
when i pulled the others the reading stayed ay 11.3

I followed the line and it went to a power block?? (below as interior) where it then had a loop to another terminal, a lead supplying power to the fuel pump switch, and lastly another lead going to the onboard welder, where the main power lead for the welder comes out.

it all loops back to the welder then, right? does that mean i did fry a diode or something?

 

[Viperwolf1]

Good work. Now pull the wire to the fuel switch and welder (one at a time) from that terminal block to further isolate the draw. It's coming from one of them.

 

[Bundy]

just because i thought it would be helpful to someone else, i thought i would follow up on this. After narrowing down to the above, i called an amazingly helpful gentlemen Yuwan at Premier Power and he gave me a series of tests for each wire terminal on welder.

As it turns out, the line coming out of the onboard welder was not keyed to the ignition so it was pulling just enough to drain the battery. in addition, the tests exposed the fact that my alternator was doing a shitty job of recharging the battery, all because my belt was loose and slipping.

So after rewiring the welder to it was keyed off the ignition and replacing belts, she will start after a week of sitting with no hesitation!