Tom,
A Major should be positive ground. Negative grounding did not come in on British Fords until the 1000'nd series.It will not matter whether the tractor is positive or negative. The problem comes when the ground is first changed. If a new battery or dynamo is installed and is the wrong match, major electrical faults occur like regulator and dynamo burning out. If however a simple action is taken all will be well. This action should be done everytime a Dynamo is fitted to any vehicle or if the battery leads have been changed around. Take a piece of wire and connect it to the output terminal of the battery. NOT THE GROUND TERMINAL. Place the other end on the FIELD (small) terminal of the dynamo and hold it there for 20 secs. The field and output wires must be diconnected and the dynamo bolted to the tractor. After 20 secs., disconnect and remove the wire you added. Reconnect the output and field wires. Drive and enjoy your tractor. What you will have done is correctly polarised your dynamo to what ever way round you have connected your battery. regards Brian
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