Message to owners of the Onan 6.5NHEFA26101D and some other NH and BG models of that era.:
Onan produced a control board upgrade kit for those generator sets, part number 300-3950. The kit includes the 300-3763-01control board, a new wiring harness, and some misc. hardware. I don't know how many of these upgrades were made by Onan, but in case you have a generator that has had its control board updated from the 3-Plug style control board (A1),to the 2-plug style, this is for you.
The reason I focus on this particular generator is that it apparently is about the last model to have "points" ignition. So, when you try to find the correct schematic, you get pretty close on either side of that changeover, but never quite right.
If your generator set works fine, you probably don't care about this, but if you try to troubleshoot problems in the control board area and if your generator has been upgraded with the above kit, good luck trying to figure the wiring out. That's because the actual wiring in the control box has been changed a lot. The wires in the kit harness are labeled well as to their destination, but you may well find that NO schematic you find will fit your machine.
That's because Onan kept changing the way they dealt with the fuel pump, and ignition circuits. I even found that, at one time, they got some bad fuel pumps and they changed either the blocking diode arrangement or the series resistor to make up for the problem. Once they changed fuel pump mfr's, its unclear to me if and when they changed the ccircuit again. You may have a schematic that shows no fuel pump series resistor, when indeed there IS one in your machine.
The only way I know to figure out what's really going on in YOUR generator is to get a copy of the Kit instructions and
apply the directions to your set.
After some searching, Dennis Risser from Advanced Service And Parts
was kind enough to supply me with the instructions,
free of charge.
I promised to make my next Onan parts buy from them.
Here's a link to the .pdf: A1 Control Board Upgrade Kit
Disclaimer:
I am no expert on anything, but I have spent many hours trying to get to the bottom of this particular issue.
Many of the true experts on the Smokstak.com Onan Forum have helped me time
and time again.
If this article has been too mystical for you, email me and I will try to answer your questions.