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Farmall & IHC Tractors Discussion Forum
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reversed polarity..

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karl f

06-13-2006 20:17:50




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my brother was talking about the weird behavior of the ammeter on our 400. i knew they put in a new battery last fall. i wasn't there when they did and my diagnosis was right. they reversed the polarity. it's a 6v pos ground system. i switched it to normal (+ ground), polarized regulator, it showed charging for a few seconds, blipped from 0 to C a couple times then nothing. shorted F to ground, nothing. did being reversed kill the generator or was it just its time?
-karl f

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karl f

06-14-2006 21:35:19




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 Re: reversed polarity.. in reply to karl f, 06-13-2006 20:17:50  
i took the generator to a local rebuilder for testing and it passed. asked them about the situation, and bought a regulator based on what they said. put it all together. grounded F, jumped BAT and GEN. Huge spark, nothing like the little thing yesterday. started tractor, shows charge of about 50% on meter at 1/3 or more throttle. a voltage reading at the battery is only at 6.5v even at full throttle though. thanks -karl
ps support the local rebuilders..they were more helpful and cheaper (but with value) than my current employer could offer me at my discounted price. i work at an auto parts store similar to napa, not one of those flashy shiny places.

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John T

06-14-2006 06:10:31




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 Re: reversed polarity.. in reply to karl f, 06-13-2006 20:17:50  
Karl, I agree with Bob in that running the genny in reverse shouldnt have hurt it, but there could have been harm done to the Voltage Regulator if things werent done correct or the genny didnt get re polarized correct.

You say you shorted the field to ground and still no charge, so AFTER YOURE SURE THE GENNY IS POLARIZED CORRECT try it again when running and the field grounded and if still no charge, leave the field grounded and by pass/jump the VR's cutout relay by momentarily connecting its BAT and Gen (or Arm) n see if she charges then?? If theres no charge with the field dead grounded and the VR's cutout relay by passed, the VR is essentially out of the circuit n she ought to charge IFFFFF THE GENNY IS GOOD along with all the other wiring etc.

POLARIZE THE GENNY FIRST BEFORE TRYING THIS

John T

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Bob

06-13-2006 20:41:40




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 Re: reversed polarity.. in reply to karl f, 06-13-2006 20:17:50  
You don't polarize the regulator. You polarize the GENERATOR (even though you may be jumpering connections at the regulator).

Polarize it again, and try full-fielding it by grounding the "F" terminal.

The generator would not have been hurt by charging with reverse polarity, but it may take a couple of attempts to get enough residual magnetism built up in the field polepieces for it to "excite" itself at startup.

An old electrical "guru" who's shop I used to hang around as a kid would sometimes tap the generator's belly in the area of the polepieces with a small brass hammer while polarizing it.

I can't certify that this helped build up the residual magnetism in the polepieces, but it SEEMED to work for him!

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