Re: (ET) Most insane ground fault ever...

[steves <ssawtelle erols com>]

If it's 7V and .004 mA that's 1.75 Megaohms. If you have a DVM, it's 
proabaly 10Mohms or more, so it's not really loading down the source, so 
that well could be some unintended metal junction battery action. Maybe 
if you can get it to rust badly enough you can do without batteries ;-).

- SteveS



Christopher Zach wrote:

> In the really strange category:
>
> I disconnected the batteries (+ and -) and I found 7 volts between frame 
> and the + wire.
>
> So I pulled out the disconnected front batteries (the old T105's, 
> ballast). Still 7 volts. At .004ma.
>
> Either my meter is too sensitive or I am watching the tractor literally 
> rust :-)
>
> Chris
>
> steves wrote:
>
> > That is strange. I guess the first thing I would do is, with batteries 
> > disconnected, measure ohms from main and lift motors wiring to frame 
> > to see if anything truly has a short and then narrow it down from 
> > there. If the main motor field has a short, it is not a big job to 
> > pull it and tear it down. You may just have a rubbing wire or 
> > something else simple.   I have never opened a lift motor, but others 
> > have - it's not too bad to get to either.
> >
> > Frame shorts make for some very interesting problems. Let us know what 
> > you  find!
> >
> >
> > - SteveS
> >
> >
> > Chris Zach wrote:
> >
> >
> > > This is going to go down in history as the most insane grund fault 
> > > ever...
> > >
> > > E20-AA type tractor. For purposes of this discussion, the headlight 
> > > wires are disconnected.
> > >
> > > Here's the symptoms:
> > >
> > > If I unplug the common wire to battery from the lift, the tractor 
> > > works. However if I toggle the lift switch up or down, the field 
> > > weakening relay closes with a *click*
> > >
> > > If I plug in the lift to the midpoint of the pack (18 volts), the 
> > > lift will go up and down. However the tractor is pulling current thru 
> > > that wire to power the tractor field with 18 volts and the cc relay 
> > > with 18 volts (not enough to pull it in).
> > >
> > > If I move the lift wire towards the + terminals, the lift gets 
> > > weaker. However the current draw increases, and at around 30 volts 
> > > the field weakening relay closes with a *click*. At 36 volts there is 
> > > no lift, relay closes, full field on tractor motor.
> > >
> > > If I move the wire towards the battery - terminal, the lift gets way 
> > > stronger fast. I don't want to go that way too far, as the lift will 
> > > burn out.
> > >
> > > All of the above only happens when the motor field is connected. For 
> > > a bonus, the drawing of current happens even when the tractor's main 
> > > disconnect is *OFF*
> > >
> > > What the HECK is happening?
> > >
> > > Chris
> > >
> > >
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> >
> >
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