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Writer's pictureAlexander Stuck

TO-20 Wiring Diagram

I have a Ferguson TO-20 or TE-20 tractor. I put on a new ignition switch and did not notice one pole touching the frame. The wires melted. Now I do not know how they were connected and cannot get it to turn over. It has red light, 6 volt system. I had been hooking the negative ground to the negative battery as that was the way it was when I got it. I ordered a new wiring harness. The wire had been spliced, taped and are in poor shape. How do I figure out how it was wired. I got a wiring diagram and manual. The serial number is 37047. Is it positive ground or negative ground by the way it is made? It was running fine before this. How do I know if it is a TO or TE-20? Any help would be appreciated. Wiring is all a mystery to me.


The serial number plate for the tractor which is located at the top of the steering gear housing should indicate if the tractor is a TE or a TO model. The first two letters of the serial number should be either TE or TO. TO models should indicate the tractor was made by Harry Ferguson Inc., Detroit, MI. TE models should indicate the tractor was built by Standard Motors for Harry Ferguson Limited in the UK. There are several pictures showing the difference between the TE and TO models on our FENA web site. All TE and TO models were 6 volt positive ground. TO models were equipped with Delco Remy generators, starters, voltage regulators and distributors. On TE models these items were Lucas electrical components. The lower steering gear housing on TO models does not include the to cover for the transmission. The transmission top cover on TO model is a metal stamping. The lower steering gear housing on TE models extends over the top of the transmission and includes the gear shift lever. This detail is shown in the first link above. As for why you tractor will not turn over, I cannot answer that other than to suggest that possibly the battery is discharged enough that it will not turn the starter over or more of the wiring is damaged. You will have to check out each component individually as well as all the wiring going to each component. Later production TEA-20 models were 12 volt rather than 6 volt. TEA models were equipped with Standard Motors engines rather than the Continental engines used on the TE and TO models.

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