From: w7ls (w7ls@blarg.net)
Date: Mon Aug 16 2004 - 00:11:51 PDT
There are some capacitors (condensers, in automotive parliance) in the system to reduce electical noise for the benefit of radio reception. Those are the ones that you are momentarily charging and seeing the resultant spark from. As for the continuous leakage, a common leak is found inside the starter button. The button shorts the bottom of the starter solenoid (very inductive) to ground, thereby energising the solenoid and extending the starter gear and finally kicking in the actual starter motor. When you remove your finger from the button, the solenoids magnetic field collapses, inducing a large reverse voltage across the button contacts and creating a flash, which is metal from the contacts blowing out onto the insulating portions of the switch housing. Over time, that builds up to form a slightly conductive path. It's too weak to engage the solenoid, but big enough to drain batteries over time.
Here's a way to see if it is your starter switch: Put your ammeter (one of the lower scales on a multimeter) in the battery line, note the drain current as you did before, and then yank the wires out of the back of the starter button on the dash. If the current fell, that's part or all of your problem. There could be other problems, too. Might unscrew the huge Cannon connector from the back of the 3 lever light switch and see if the drain current falls. That would at least tell you if the drain was in the lighting circuits.
Good luck. Let us know. Jim
On Sun, Aug 15, 2004 at 7:48pm Alex <alex@glx.net> wrote:
> So like a good boy, I keep taking the ground terminal off the battery
> set when I'm not around and/or not going to be working on the truck.
> When I go to put it on, I see a small spark. I remember reading on the
> list a while back about someone doing the same and thinking it was due
> to a discharged capacitor somewhere (?). and it was only the charging
> that was taking place. Being somewhat anal about drain on some very
> expensive batteries, I put a digital VOM on and found a constant drain
> of about 80ma. I haven't had a chance to disconnect the Prestolite
> alternator yet. You guys think that's it? Diode leakage? Is it too much
> drain? Any suggestions? Also where is a good out sight place to mount
> one of those marine battery disconnect switches?
> Thanks,
> Alex
>
> PS an epilogue to chapter 1 and a new chapter 2 are coming soon.
>
>
>
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