Does anyone know why some of the older tractors batteries are positive grounded? How would I jump-start one?

-- Keith (halfc@fidnet.com), November 27, 2001

Answers

In DC electricity electrons flow from one polarity to the opposite polarity. It does not matter which one is designated "ground" as long as it is consistent within the specific application. To change it would be necessary to modify the charging system, generator, for the desired polarity. I believe that is a fairly simple change, but in fact, have not reviewed any circuits to insure accuracy of the simplicity of the change.

-- Joe (CactusJoe001@AOL.com), November 27, 2001.

Negative jumper cable from negative battery terminal on running vehicle to negative battery terminal on tractor. Positive jumper cable from positive battery terminal on running vehicle to bare metal on tractor. My old '57 Massey Harris was positive grounded. It had set long time when I got it so wiring was beyond use. I replaced old 12v generator with 70's era GM alternator with built in voltage regulator. This required making it negative ground. Just swapped battery cables so positive cable went to solenoid and negative went to frame for a ground. Ammeter on tractor was beyond use, but if I had kept it, would have had to swap wires going/coming from back of it.

Some old Chrysler products and some older foreign cars were also positive grounded. By old, I'm talking '40s-'50s era. Some positive grounded '60s foreign cars. I'm not sure why it was done. Maybe some theory about galvanic corrosion???? Really doesnt matter. Just the way the engineering winds happened to blow. If the majority of manufacturers had chosen positive ground, we'd be talking about how to convert those oddball negative grounded vehicles. I only changed from positive ground on my tractor because I wanted to use modern alternator.

-- HermitJohn (hermit@hilltop_homestead.zzn.com), November 27, 2001.

You just start it the same way you jump start a negative ground vehicle. positive to positive, negative to negative. If you using a another vehicle to jump the tractor MAKE SURE its not touching the tractor.

-- Gary (gws@columbus.rr.com), November 27, 2001.

Forgot I also replaced ignition coil on my tractor. One on tractor was junk and couldnt read any markings, but assume it was marked opposite to coil on negative ground coil. If positive ground coil had been ok, may have had to swap terminals, I'm not sure. I dont remember anybody with positive ground vehicle having to buy a special replacement coil, but then most positive ground vehicles were 6volt and thats a long time ago. I just dont remember.

-- HermitJohn (hermit@hilltop_homestead.zzn.com), November 27, 2001.

Thanks Guys...I managed to get the tractor started without blowing my battery up.

-- Keith (halfc@fidnet.com), November 27, 2001.

Won't the starter turn backwards if you just switch the polarity and change to an alternator? I have an old Farmall that's positive ground and have not changed over to a alternator for that reason. Anyone know?

-- Dave (drcomer@rr1.net), November 29, 2001.

Dave in order to make astsrter run backwords the field coils have to be turned around so by going from + or - ground that alone will change the starter rotation {the coils are in the starter}

-- bob vadnais (robertvadnais@aol.com), December 01, 2001.

Arrrh, did I read you right there Bob, are you saying that changing the polarity WILL reverse the starter motor direction? Won't reversing the polarity also reverse the armature current direction?

-- John Hill (john@cnd.co.nz), December 01, 2001.