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Bob M
Well-known Member
Most likely your existing alternator is a Delco 10DN (externally regulated). And I suspect from your description I suspect your 72 amp alternator is a 10SI (internally-regulated).
How to tell the difference: An externally regulated alternator's aux connector has its terminals parallel (like this: I I) and labelled "R" and "F". The connector plugs straight into the back of alternator.
An internally-regulator aux connector has two terminals inline (- -), and labelled "1" and "2". It plugs in to the side of the case at the rear of the alternator.
Switching from alternator type to the other is not difficult. You simply remove the old regulator then jumper a couple wires at the regulator plug.
Incidentally if the existing system is set up for POSITIVE ground (unlikely) the changeover is a bit more complex.
Allan in NE
Well-known Member
Question is, does it have a cab with heat and air? If so, you need the big alternator; think they are around 105 amp.
Allan
"How to tell the difference: An externally regulated alternator's aux connector has its terminals parallel (like this: I I) and labelled "R" and "F". The connector plugs straight into the back of alternator."
"An internally-regulator aux connector has two terminals inline (- -), and labelled "1" and "2". It plugs in to the side of the case at the rear of the alternator. "
I have a 10SI on my bench as we 'speak' which has both numbers & letters cast into it, 1, 2 and F, R. I have seen other 10SI units that have F & R as well. Probably has to do with when cast. May be a hold over from an earlier application that used an external SS regulator? For whatever reason, all three kinds of markings are out there.
Bob M
Well-known Member
There's also a 4th terminal marking variation for the 10 SI: LAMP and SENSE. The 10SI on my Super M is so labelled. (Incidentally also this alternator is marked "made in France")
However most (all?) the aux terminals on later production 10SI alternators labelled simply 1 and 2.
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And there's a variation for the Delco 10DN: On my '63 Oliver 1650 the aux terminals are marked RELAY and FIELD.
When rebuilding my 856, I converted from the stock external regulator 10DN and substituted internal regulator 10SI alternator.
I made a jumper wire with a male blade connector on each end. The wire needs to be long enough to plug into the outermost terminal at each end of the regulator plug.(in the compartment down by your feet, remove the external regulator) This will connect the charge light to the field wire. Buy a SI series harness repair plug from an auto parts store to fit the 10SI alternator. Put a ring terminal on the #2 (red)sense wire and connect it to the Big "bat" stud on the alt rear. Splice the field wire in the harness to the #1(white) excite wire on the 10SI alternator plug. Tape up the "R" wire in the harness as it is no longer used.
Connect the heavy harness Bat wire to the alternator BAT stud.
The tractor is now wired for a working charge light with the internal regulated 10SI alternator.
They had an odd brush holder assy that brought the brush (F) terminal, and the stator(R) terminal up to the side regulator plug location. The regulator plug hole was shaped a bit like a chevy bowtie emblem, in that the center of the slot was larger in the center so either the little(II) external regulator alt plug, or the long (- -) internal regulator SI type plug would fit. I dont know if these oddballs alternators were used during the 10 DN to 10 SI change over, or if they were a replacement for external regulator cars that originally had the 10 DN ??
When I found one of them at the junkyard, I just substituted an internal SI regulator and diode trio, and had another instant 10SI. That had to be why those early SI type cases had both the R F and the 1 2 on the same case. Also, those for export had the L (lamp) and S (Sense) markings.
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