Re: wiring for 12-volt conversion 1940 Farmall B

Posted by Bob M on February 16, 2004 at 12:04:24 from (165.170.128.65):

In Reply to: wiring for 12-volt conversion 1940 Farmall B posted by Jimmy on February 16, 2004 at 11:14:14:

Jimmy - A couple things going on here:

Since your tractor electrics are now negative ground (it came from the factory positive ground) you'll need to reverse the connections again at the ammeter to get it to read correctly.

The alternator as you describe it is an early Delco externally-regulated unit. It must have a regulator and other circuitry (warning light or resistor) connected to the R and F terminals for it to work. A true single wire alternator on the other hand will have an opening on the back for aux terminals labeled 1 and 2, but the actual terminals will be missing or the opening plugged.

You've got several options here:

1 - Get the matching voltage regulator for your current alternator and wire it up, including adding a warning light/resistor. Not terribly difficult to do.

2 - Swap the alternator for a 10SI internally regulated alternator and add the warning light/resistor wiring.

3- Swap the alternator for a true "single wire" alternator.

#1 and #2 will cost about the same when you are finished - and both will work fine. #3 will cost more (single wire alternators run usually about double the price of the 3 wire units). Also there's a risk you're B's motor will not spin a single wire alternator fast enough to get it to "turn on" and begin charging at startup - a characteristic inherent in single wire alternators.

Hope this helps! ...Bob M(elville)

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