originally tractor was positive ground, 12 volt. there is nothing wrong with connecting it negative ground, but you generator and voltage regulator will not work. if it has been converted over with "new" parts you are o.k., if not, the regulator is fried, and possibly the generator. toi test generator, remove both wires. ground the "F" terminal. start tractor and measure voltage output across the "A" to "F" terminal. if you have 20 volts or so, the generator is o.k., now is the "A" putting out negative or positive on the volt meter. if it is negative, you have the original generator, if it is positive it has been converted over to the newer negative gound type. The "A" terminal can be connected to the "HOT" side of the battery, that is not grounded and will then put out a more constant voltage (14 volts) and full current (20 amps), unless the voltage regulator is put into the system.