Help locating voltage/amperage draw when off.

CommrclDiver · Post by **CommrclDiver** » Sat Oct 05, 2013 11:04 am

1971 F100 LWB Custom. Battery dies after 3 days sitting. Battery is new and test good. Any ideas in where to start?

sargentrs · Post by **sargentrs** » Sat Oct 05, 2013 4:27 pm

I'd start with the headlight switch and the ignition switch.

chad67 · Post by **chad67** » Sat Oct 05, 2013 6:54 pm

I had a Mustang with the voltage regulator built in to the alternator that did the same thing. Something in there would get stuck every once in a while, like 3 times a week, and kill the battery. I'd look at the regulator and alternator, but only because of my personal experience.

fmartin_gila1 · Post by **fmartin_gila1** » Sun Oct 06, 2013 7:41 am

Disconnect the + terminal and put a test light between the cable and the terminal. If it lights up, you have a draw. It will go out when you disconnect wherever the draw is.

Fred

Mach428 · Post by **Mach428** » Mon Oct 07, 2013 8:56 am

I JUST fixed this same problem with my Mustang. Turns out that the ignition switch would not always disengage the electrical system when turned off. I went through EVERYTHING and finally through process of elimination found the switch was bad. Replaced the switch and now she can sit for weeks and start right up.

Nitekruizer · Post by **Nitekruizer** » Mon Oct 07, 2013 12:48 pm

chad67 wrote:I had a Mustang with the voltage regulator built in to the alternator that did the same thing. Something in there would get stuck every once in a while, like 3 times a week, and kill the battery. I'd look at the regulator and alternator, but only because of my personal experience.

The external voltage regulators can also go bad and cause the battery to go dead while the car/truck is sitting. I've had several of the electronic VR's do this. The bad VR lets the power drain back through the alternator's field windings.
Yes, connect a 12 volt test light between the battery cable and the battery post. Try removing one fuse at a time to find the voltage drain. When the light goes out you've found the problem circuit. If you don't find a circuit that is draining the battery, try unplugging the VR with the engine not running. If the light goes out try another VR.

CommrclDiver · Post by **CommrclDiver** » Fri Oct 11, 2013 1:34 pm

I love this place!

chad67 · Post by **chad67** » Fri Oct 11, 2013 8:24 pm

Any luck getting this one solved?

CommrclDiver · Post by **CommrclDiver** » Sat Oct 19, 2013 10:52 pm

Turns out it was my tach was wired in 12v constant. Wired to 12v keyed and voila no more draw.

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Help locating voltage/amperage draw when off.

Help locating voltage/amperage draw when off.

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