Fordson Major diesel -12 volt -positive or negative earth

Rolls · Nov 23, 2012

Hi Guys.

I believe I have a 1956 Fordson Major(S/N 1298033 or 55) which was gratefully given to me by my brother in-law, which he purchased some years ago.

It has been reconditioned (motor) and reprayed, but the electrical system seems to be all over the shop. All the head light wiring has been cut and it is not charging the battery.

I"m a little confused(which isn"t hard to do) as I have 2 workshop manuals, both say that the tractor is positive earth, I have checked and double checked and my tractor and it is negative earth.This may be the reason the headlight wiring is disconnected and why it is not charging.

On that note, how does it charge the battery, as it appears that the positive terminal from the battery goes to the starter motor and the negative is earthed to the body. There are no other wires going from the regulator to the battery.

Any idea"s

Cheers
Rolls

Mike Farmer · Nov 24, 2012

Hi. If you go to the archive on this site. Search for Fordson Major Wiring. Go page 2 item 32 and work back from there. I posted several wiring diagrams. I've just checked em out and they still appear to be ok. If that doesn't work I will email them direct to you. Mike

Mike Farmer · Nov 24, 2012

Sorry forgot this. It comes up as July 1954

Rolls · Nov 24, 2012

Thanks Mike.

I have the diagram,but this is also saying it is a positive earth. I"m not sure if my battery is connected correctly (negative earth) but it will start with a jump start. Could this do damage starting it connected to negative earth ?

Cheers
Rolls

Robert Major · Nov 24, 2012

Hi
when the tractor was new it was positive earth, Many have been messed with over the years and changed negative. it will not hurt the starter the other way round. all you have to do is re wire the system and polarize the dynamo the correct way for what you choose .
If you fit an alternator instead like common off the shelf G.M.C internal regulator type , you will have to go neg earth to get it to work.
when your done mark the way earth is under the hood so the next guy knows, I have a few here I have bought, with mangled terminals and got to check the wiring to find out what they are wired.
Regards Robert

Rolls · Nov 26, 2012

Hi Robert.

Thanks for the advice,as far as I can find out it is should be positive earth. When I get a chance in the next week or so, I will swap the terminals back to positive earth and see how it goes.

Thanks again.
Rolls.

Mike Farmer · Nov 28, 2012

Hi I've Re read this whole item. Yes it should be positive earth--BUT-- Your statement "it will jump start". OK. Thats probably the reason the earth has been changed. Because its seriously bad news trying to jump start a positive earth vehicle from one which is negative and I would suggest that a negative one is usually more easily available, so dont change it back whilst you still need this facility. If you want to convert it properly no problem. either change polarity on the Dynamo or fit an alternator as previously suggested then change the wiring arond on the ammeter. Ignore the starter motor. Mike

Rolls · Nov 29, 2012

Thanks again Farmer Mike. I will look into getting changed over to negative earth and fitting a alternator.

Cheers
Rolls

Fordson Major diesel -12 volt -positive or negative earth

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