Negative gounding

Hello All, I have a few older tractors, JD 60, Oliver 880, Farmall 450. Can someone please explain how "negative grounding" works, and how do I know if my tractor is negatively grounded or positive? Thank you in advance.

easy just look at which battery cable runs to ground.

Positive ground or negative ground refers to the battery connections.

Looking at the battery posts, if the larger, "+" post is connected to the grounded cable (the one bolted to the engine block or the sheetmetal), it is a "positive ground".

If the smaller, "-" post is connected to the block or sheetmetal, it is a "negative ground".

If the battery has been removed, and the polarity is not known, you can usually tell by looking at the coil connections. If the "-" terminal is connected to the ignition switch, and the "+" terminal is connected to the points, it is a positive ground. There may also be markings on the regulator refering to the polarity.

Most positive ground systems are limited to the older 6 volt systems.

If the generator has been replaced with an alternator, it will be a negative ground.

(There are a very few exceptions to this though! Some factory alternator systems are positive ground. If in doubt check the manual, connecting an alternator equipped system backward will cause damage.)

Connecting a generator equipped system backward should not cause damage, but it will not charge properly.

Your tractor were pos gnd and so were the regulators made for pos ground so keep pos gnd unless you get neg ground regs and polorize the gen for neg gnd.

Normally 6 volt tractors were positive ground (+ post of battery connected to frame), and 12 volts were negative ground (- post of battery connected to frame).

(quoted from post at 22:34:53 06/28/14) Hello All, I have a few older tractors, JD 60, Oliver 880, Farmall 450. Can someone please explain how "negative grounding" works, and how do I know if my tractor is negatively grounded or positive? Thank you in advance.

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Technically it's positive or negative chassis. There is no GROUND rod driven 10ft into the earth and connected to the tractor.

Usually the only part of a tractor that "cares" if hooked negative or positive to chassis is the voltage regulator and somewhere it will be marked.
The exception is the "convertible" regulator. 2nd to that is a few ignition coils that were polarity sensitive and put out less max spark potential if hooked incorrectly. Again if you have such a coil - it will be marked.

John Deere continued using positive ground on 12V systems for the first of the New Generations. e.g. My "64 2010D as well as a friend" 3010D are 12V positive ground.

"Can someone please explain how "negative grounding" works"

Negative Grounding is when the batterys Negative post is attached to frame ground while Positive Grounding is the opposite. The return current for loads like the starter and lights and ignition etc can use the tractors conductive iron frame (often referred to as Ground) so you only have to run one wire to them. The frame sort of acts as the other wire

Many old 6 volt tractors were originally Positive Ground and then when they converted to 12 volts many switched over to Negative Ground. Two cylinder John Deere 6 and 12 volt tractors, however, were all Positive grounded.

"and how do I know if my tractor is negatively grounded or positive"

You can see which battery post, Pos or Neg is frame grounded, however, some got changed over the years.

A typical old tractor generator works at EITHER polarity provided its correctly Polarized. It dont care which battery post + or - is tied to a huge rusty chunk of iron lol

Some Voltage Regulators are labeled for Pos or Neg ground while others may not be.

A typical tractor coil is Polarity sensitive and should be used as labeled + and -. If its Neg ground the - wires to the distributor while if Pos ground its + wires to distributor. It can still produce a spark at either polarity but its more efficient if used correctly as labeled.

Got it???

John T

Not necessarily; Case tractors built at Racine were 6 volt negative ground and those built at Rock Island were positive.

Seems I always forget something grrrrrrrr

In addition to Ignition Coils and many Voltage Regulators, yet another item that cares and is sensitive to what polarity is used (Pos or Neg) is the Ammeter. It also has + and - terminals and if wired incorrect it would register just bass ackwards, i.e. would show + charge when discharging and - discharge when charging. If that's the case simply reverse the wires.

SUMMARY: Ignition Coils, Voltage Regulators, Ammeters are usually polarity sensitive. The typical old tractor Generator can still charge at either polarity once correctly polarized. The typical old tractor starter, however, still turns the same direction at either polarity.

Probably more I forgot so no warranty

John T

Nice little tidbit of trivia for Case fans. I wasn't aware of that. I guess that example would be considered NOT normally under the posters statement.

John T