farmall 400 switchover from pos ground to neg ground

tim carr · Aug 15, 2009

I recently put on an alternator with built in regulator but this tractor has an external regulator also. So do I need to completely remove
external regulator and also run a ballast resistor. The tractor is a 12 volt system now with neg ground. I took off the generator and switched this system from pos ground to neg ground. Any help or suggestion would be appreciated. Thanks!!!

Nebraska Kirk · Aug 15, 2009

(quoted from post at 21:12:26 08/15/09) I recently put on an alternator with built in regulator but this tractor has an external regulator also. So do I need to completely remove
external regulator and also run a ballast resistor. The tractor is a 12 volt system now with neg ground. I took off the generator and switched this system from pos ground to neg ground. Any help or suggestion would be appreciated. Thanks!!!

Remove or unhook the external regulator. If your coil does not have an internal resistor then you will have to add an external ballast resistor.

Bob · Aug 16, 2009

For (+) ground, the coils (+) terminal was connected to the distributor.

After the conversion to (-) ground, the connections need to be swapped so the coil's (-) terminal goes to the distributor.

Brian Bell · Aug 16, 2009

As far as the regulator, you should be able to unhook the old one and run a wire from the big terminal on the alternator straight to the battery. I'm using a Delco 10SI on my 8N this way.

John T · Aug 16, 2009

Tim,

QUESTION
"I recently put on an alternator with built in regulator but this tractor has an external regulator also. So do I need to completely remove
external regulator"

With a totaly internally regulated alternator NO DO NOT use any other external regulator especially NOT any old one for use with a generator. The wire down from the ammeter in dash that used to wire to the BAT terminal on a Voltage Regulator now wires instead to the Alternators big main output stud. When I upgrade to an alternator however, I upgrade that wire to at least No 10

QUESTION

"and also run a ballast resistor".

Whether or not you need an external series voltage dropping (12 to 6) ignition ballast resistor depends on what coil you have. If its a 6 volt coil YES one is needed, however if its a full true 12 volt coil (some folks call them internally ballasted) none is required

If the tractor had an ammeter and you switched from Pos to neg ground its leads need reversed or it will register bass ackwards. Bob has ya covered on the correct coil polarity wiring

John T

farmall 400 switchover from pos ground to neg ground

tim carr

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Nebraska Kirk

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Bob

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Brian Bell

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John T

Well-known Member

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