Allis C model, positive or negative ground?

[09112]

I have what I believe to be a 1949 Allis C engine that I put onto a B frame. It has an alternator and I'm not sure if it is positive or negative ground. Anyone out there have any views on this? What would the ramifications be if I reverse the set up and how will I know if it is correct? Really a rookie at this stuff as you might know. Electrics give me nightmares.

 

[Clint S]

Positive ground way back when, but who knows now. The tractor or the alternator don't really care which one it is.

 

[RickB]

Positive ground way back when, but who knows now. The tractor or the alternator don't really care which one it is.

Actually, alternators care quite a bit about polarity.

 

[Wagtail]

TractorData.com says that the 'C' is a positive ground.

 

[RickB]

TractorData.com says that the 'C' is a positive ground.

Little doubt it was, 70 years ago or so. But it didn’t have that pesky alternator then. There’s about a 95% chance the alternator is negative ground.

 

[09112]

Thanks for the input guys.

 

[WranglerX]

If running alternator, it's probably going to be negative ground..... Starter and alternator care most of the other electrics don't....

Dale

 

[RickB]

If running alternator, it's probably going to be negative ground..... Starter and alternator care most of the other electrics don't....

Dale

Starters are not polarity sensitive. To a large degree they are insensitive to higher voltage than they are wound for. Don’t fool the guy into buying a starter he doesn’t need by posting inaccuracies.

 

[WranglerX]

Starters are not polarity sensitive. To a large degree they are insensitive to higher voltage than they are wound for. Don’t fool the guy into buying a starter he doesn’t need by posting inaccuracies.

Was not trying to fool anybody... Only trying to make OP aware there "may" be problem with starter, not that there actual would be....

Dale

 

[RickB]

Was not trying to fool anybody... Only trying to make OP aware there "may" be problem with starter, not that there actual would be....

Dale

“starter and alternator care”

 

[WranglerX]

“starter and alternator care”

Ok just like burger king.... HAVE IT YOUR WAY........

Dale

 

[tomplum]

Won't the starter run backwards with the polarity reversed? That could give a clue.

 

[RickB]

Won't the starter run backwards with the polarity reversed? That could give a clue.

It will not.

 

[100 td]

Won't the starter run backwards with the polarity reversed? That could give a clue.

This one won't, but for clarity/future reference, if it's a permanent magnet starter motor as on a lot of smaller engines, they will. But of course 99.99% (I guess) of things that run with a starter with permanent magnets, are all negative ground.