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

[Christopher Zach <czach computer org>]

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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