The past two weekends and evenings in between, I have been swapping out my old, dependable, but high hour Onan Power drawer for a "fully reconditioned" one that came from Kerry Tandy's coach, through Steve Ferguson. Should be 'plug-n-play' right? Not really. There were several minor problems with the 'new' one that I spent numerous hours fixing, but the main issue was the remote start wiring.

After hooking it up the way it was originally (I thought), it didn't work. A number of things were not right on the connections to the control board, but I was able to figure that out from the manual. The next issue was that the color codes on the end going into the coach, were different. With a lot of help from my son and a multi meter, we finally got it right and everything works the way it is supposed to.

My question concerns the wire that provides power to the Hobbs meter and the switch light. On both generators, this wire had a ring terminal on it and was connected to the + terminal on the coil. The wiring diagram shows it connected to pin #6 on the control board. Is there a preference on this connection? It seems to work properly either way, even with the prime circuit.

Thanks,

Carl,

Whether you connect to the board or a connected device matters almost as
much as whether you tie your shoes overhand or underhand. But be sure you
connect to the correct location. Pin 6 is definitely NOT that. Pin 9
would be OK, but that connects directly to Coil +, so why not stick with
that?
http://www.gmcmhphotos.com/photos/onan/p39734-kh-redrawn-onan-schematic.html

Ken H.


On Mon, May 29, 2017 at 7:20 PM, Carl Stouffer wrote:


> My question concerns the wire that provides power to the Hobbs meter and
> the switch light. On both generators, this wire had a ring terminal on it
> and was connected to the + terminal on the coil. The wiring diagram shows
> it connected to pin #6 on the control board. Is there a preference on this
> connection? It seems to work properly either way, even with the prime
> circuit.
>
> Thanks,
>
>
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
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That makes perfect sense, Ken (except for the part that pin 6 is definitely NOT it, since the diagram in the manual shows the connection to pin 6). The generators, both of them, were wired to the coil from the factory, by Onan.

Unfortunately for me, the harness was cut just below the plug on the Onan side, and the plug had been bypassed on the other end. There were bits of wire on the butt connectors, but they didn't seem to match up to my wiring. My coach is a '75, and Kerry's is a ?? so there was evidently a difference in the harness going to the remote panel.

Thanks,

Carl,

By Golly, you're right! Onan's diagram DOES show 6=9 and I've got it
connected to CR5+CR7+R2 -- an obvious error I've propagated for the past
15+ years (without previous complaint). There's another error too, less
egregious than this one, that I'm hoping Mr. ERF will remind me of again.
Guess I had even more trouble reading the Onan schematic than I realized!
I'll try to find the program I used to create that drawing and correct it.

By the way, when I had an Onan, I rewired it using about 1/3 the OEM wire
-- there are a lot of, IMHO, dumb connections on there -- even without
changing any of the functionality. Some places I found 18" of wire where
6" was more than adequate.

Ken H.

​O​
n, May 29, 2017 at 8:24 PM, Carl Stouffer wrote:

> ​...
>
> That makes perfect sense, Ken (except for the part that pin 6 is
> definitely NOT it, since the diagram in the manual shows the connection to
> pin 6).
> The generators, both of them, were wired to the coil from the factory, by
> Onan.
>
> Unfortunately for me, the harness was cut just below the plug on the Onan
> side, and the plug had been bypassed on the other end. There were bits of
> wire on the butt connectors, but they didn't seem to match up to my
> wiring. My coach is a '75, and Kerry's is a ?? so there was evidently a
> difference in the harness going to the remote panel.
>
>
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Ken,
I guess if a guy with your knowledge and qualifications had trouble reading the Onan schematic, I can see why I was COMPLETELY lost. My dad was an EE, but it definitely didn't rub off on me! I guess I'll connect the wire in question to pin 6. The only reason I asked was that it seems like there was a pulse in the voltage on the + side of the coil when reading it with the VOM. Maybe it won't make any difference. Just seems strange that GM says to connect it to pin 6 and Onan wired it directly to the coil.

Carl S. wrote on Mon, 29 May 2017 22:00

Ken,
I guess if a guy with your knowledge and qualifications had trouble reading the Onan schematic, I can see why I was COMPLETELY lost. My dad was an EE, but it definitely didn't rub off on me! I guess I'll connect the wire in question to pin 6. The only reason I asked was that it seems like there was a pulse in the voltage on the + side of the coil when reading it with the VOM. Maybe it won't make any difference. Just seems strange that GM says to connect it to pin 6 and Onan wired it directly to the coil.

Onan never connected it to the coil. Onan connected it to pin 6. Someone who worked on it after it came from the factory stuck it on the coil.

The 6 pins across the top of the board are for the remote panel.

1 is ground.
2 is start.
3 is stop.
4 is not used in our application.
5 is for a battery condition meter.
6 is for the "generator running" indicator and the Hobbs meter.

Not as far as I can tell. Both Onans had the pin 6 wire connected to the coil with an un-modified wiring harness, exactly the same way. Sure looked like a factory installation to me.

I've installed the 'contractor' version (different manifolds, a bit taller and higher output, 120/240 alternator, in remoted stuff. With the feed taken off the coil factory new.

--johnny

I've installed the 'contractor' version (different manifolds, a bit taller and higher output, 120/240 alternator, in remoted stuff. With the feed taken off the coil factory new.

--johnny

I haven't stared at the schematic for the Onan board long enough to know reality, but two things I know: One is that pin 6 should only have 12VDC on it when the generator has reached speed (and the board thinks it is running). The second is that the coil + has 12VDC on it as soon as the start switch is pressed. Without looking at the schematic, the coil + and pin 6 might be electrically identical. But...

It doesn't seem right that the "run" indicator lamp should come on as soon as the start switch is engaged. It will if it is wired to the coil. It should come on after the flywheel alternator spins up.