Positive or Negative Ground

[GWheat]

This Ford 4000 was converted to 12v at some point in time. The main issue is I don’t know how to tell whether it’s a positive or negative ground. Here’s a couple of photos I got this morning before the rain set in.
Any tips or ideas are appreciated.
Thanks

 

[RickB]

3 cylinder or 4 cylinder 4000? Alternator or generator?

 

[GWheat]

Good old 4 cylinder. Currently has a alternator on it. It’s wired, but that’s one of the issues that’s with the tractor. Or so I was told.

 

[RickB]

All but certain to be negative ground. There’s few alternators in the world set up for 12V positive ground and no good reason to use one on that tractor.

 

[Industrial Toys]

If you have an alternator, presumeably you don't have a seperate voltage regulator so, one less thing to consider for voltage and/or polarity.

 

[RickB]

If you have an alternator, presumeably you don't have a seperate voltage regulator so, one less thing to consider for voltage and/or polarity.

You could bump the starter with a positive jumper cable and see if the fan goes the right way.

Starters are not polarity sensitive.

 

[Industrial Toys]

Edited, so as not to give bad information.

 

[RickB]

It's a DC motor. If you put reverse voltage to it, it will spin backwards.

Not so.

 

[Industrial Toys]

I may stand corrected. BUT, I have never seen a brushed DC motor that would not go backwards with reversed polarity. It does make sense though. You change the rotor polarity and the stator as well, so end up the same. So, every motor I have played with has likely had a permanent magnet for the stator???

 

[GWheat]

Here’s a picture of the alternator fellas. Not the greatest picture. Raining and bit cold today.
Name on the bottom is Delco Remy