Gen Set 24vdc alternator help wanted

I am likely suffering from a brain lapse, but here goes. my 100kw 007B has a 3 wire 24vdc belt driven battery charging alternator, it is a self regulating 3 wire type, 2 each #12 wires and a #16 the two larger wires go the + and - to help charge the battery system, where does the smaller 3rd wire go. If i ever knew I have forgotten.

A part of me thinks this is what I would call the sensing wire where it also would go to a + point in the battery charging/voltage sensing scheme sampling battery voltage and directing the alternator on how much voltage output to produce to keep the battery's charged. I seem to remember this is fed from a location that is not always fed with + voltage, but only when the engine is running and then it is fed onto a + point after the engine has started and will then sense the battery voltage and typically provide recharging to the batteries and as well supply voltage for the sets control logic during operating periods. Can anyone enlighten me better or help me land this wire and make this work as intended.

As a possible question ? yes the alternator was working fine when I removed all the old analog controls and systems, but yes I didn't trace out the system and the typical schematic wiring diagram on the door panels is not much help at all it conflicts it self in several critical places and should not be trusted.

As a side note the newer 80X series schematics are vastly improved and much easier to follow.
thank you: mac/mc

I think your third wire is for excision. I will look later, but I think that's it.

Guy so we're on the same sorta page, you're saying excision with the implication it is used to sample battery or really dc control logic voltage ? thus telling the alternator to make more volts and as the [example] batteries will need a brief time to recharge after a starting effort has been accomplished, then to continue to make slightly more voltage that the fully or near charged batteries, thus being able to run the control panel, governors and all the smaller always on items once the gen set is up and running. That is my quick overview of how I recall the ckt being used, but in looking at the schematic plate on the gen set door, it gets confusing as this 'sensing' or excision wire in one trail goes to ground and in another goes to a plus point that becomes hot once the set is started and it think its the oil pressure switch that must close before this wire then sees plus voltage to sample against and feeds back to the alternator to make less or more voltage till conditions equal out within the batteries and then just make slightly more voltage to carry all the other logic demands that keep the set running and gages and the like working and indicating .. am I adding more confusion and not helping and should just sit back and be quiet.. best: mac/mc

Thought I'd try and learn something this morning, but I have trouble with electrical diagrams. That said....... Guyfang has posted the electrical diagrams for this machine here: https://www.steelsoldiers.com/attachment.php?attachmentid=683082&d=1496396655

On page 5/6 in the lower right corner it shows the "DC ALTERNATOR" connected to 3 wires.
1) Between CB1(Circuit Breaker, DC) and A16 (Heater Control),
2) Ground, and
3) Between S9-3 ( Overspeed) and K1 (Relay, Stop-Run).

Your looken at FO2. J43, pin Pin b wire goes to CB1 eventually(charges the batteries; Pin C wire P55N eventually goes to ground. Pin A wire P80J seems to be the issue. Yep it goes off the left side of the page. It wonders to J3 Pin r changes to wire P80F and if you check FO 5 several pages later you find this is the excitation of the alternator from the overspeed switch S9-3, that also goes to the Fuel solenoid and the K1. Please check lower right side of that FO-3 and you will find TB3 term 6 and this is where it all connects together. You see P80F at the bottom of the page. One of the nice things about the 100KW we all just love.


This is the answer Obi Wan sent me.

well I had followed this in the 6 pages of schematics and then ran short on time and when the wire just ran off the top left of the page, I went to bed. Indeed this series of DOD schematics was not their best effort. But at the end of it I think we agree this is the WIRE we want to set up the alternator's output. now in my instance I took off all the original logic equipment and items including the control panel. I left 3 things engine/generator radiator and most of the enclosure and went all digital logic/controls including volt reg and new precise GAC governor, as it happens I left the oil pressure switch because I ran out of oil rail plugs, I omitted trashed all the cartridge filters and went full spin for the fuel/oil systems..
So my point ? Now that you helped determine we need + I will pick up plus + sensing point when the AC voltage becomes stabilized, I have several functions that come into play and a pick off point in that scheme will be easy. So thank you much for the drawing set of prints ..I will have these blown up a few sizes and keep in the 007 file. My contact is likely going to want another 100kw for another station coming soon. Thanx Guy mac/mc

What battery group and cca should you use on a 007b?