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Negative or positive ground

B

BigTone

Member
Tractor has a alternator and a magneto, the battery was missing when I got the tractor. Is there a way to tell neg or pos ground? Does alternator automatically mean 12 volt negative volt? Thanks, Anthony
 
99% of the time an alternator will be negative ground. One sure way to know is if you hook it up backward it will start smoking fast then you can unhook it. Only alternator I have ever seen that was + ground was an English Lucas brand alternator. So unless it is a Lucas I would hook it up negative ground and if it is a Delco for sure negative ground or it will smoke guess how I know that one LOL
 
With the Alt disconnected, but bolted in place, a test light (only) will light up if connected to battery non ground terminal and the Big post on the alternator if it is wrong for the alt. If the bat is put in negative ground, and the light comes on, it is a positive ground alternator. (not likely) If the light stays off it is negative ground, and will work as is. If the alternator is shorted internally or has a shorted diode, it will also light the light. Jim
 
Awesome thanks Jim !! Great to hear from you, sad story my ex wife took the M you helped me so much with in our divorce, smh, took a couple years to get a new tractor (basically a super a with some parts from an A and a late c-123).
 
So Jim how many + ground alternators have you seen?? My self I have only ran into them on English cars that I had over the years
 
On english Lucas prince of darkness, and converted Delco (2) and on Generators converted to alternators (pricey) Jim
 
(quoted from post at 15:08:21 07/20/17) So Jim how many + ground alternators have you seen?? My self I have only ran into them on English cars that I had over the years
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A neighbor of mine had an H with a 12V positive ground Delco 10SI. That is the only one that I have worked on.
 
I agree with the talk about 99% with alternators are negative earth.

I do wonder why any bone head person would put a positive earth alternator on, instead of just switching the battery cables.
 
Well if your where across the pond in England you would know the answer to that over there a lot of stuff was + ground at least up into the 80s. Had an Austin America car and it was a + ground and never could find a radio for it because they where all - ground and to hook one up + ground you fried it
 
(quoted from post at 15:08:21 07/20/17) So Jim how many + ground alternators have you seen?? My self I have only ran into them on English cars that I had over the years
Click to expand...

The old Autocar tractor(1972) was alternator with positive ground
 

It was American iron, could have been a Lucas alternator too.

I think all white motors stuff was pos grd till Volvo got into it.

It seem the White cab over was pos grd too.

I had it off once for repair too but that was about 1980 and have not seen the truck since about 1990.

I do wish I had it. It was about the tractor I ever drove.
 
Delco made positive ground alternators. On the externally regulated, I don't think it even required any different parts -- just swap the diodes. They probably used a different regulator.
 
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