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Fairbanks Morse W3S

RodneyBates

Subscriber
Last Subscription Date
07/09/2019
I have a Fairbanks Morse W3S which runs great by starting manually. It has a magneto. Someone has changed the control board (removed it!) and wired direct. It does generate 115 volts AC and 32-36 volts DC, however checking the DC output, the positive is grounded. The plate says to use 32 volt battery. It does have an amp meter (disconnected) and a start and stop buttons (disconnected) but does not have a rheostat next to the meter. I would like to rewire so I could start it with batteries (as I'm getting worn out manually cranking) I have a wiring diagram for a W3S Onan, but it calls for a 12 volt battery. Is the 32 volt wired differently? If so, does someone have a diagram for the 32 volt? Thanks for any help you can give!
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
I have several W series and I’ve never seen or heard of a 32v DC model... can you post a few pics? Seems like an odd combination of magneto/electric start also, the electric start models usually have points and dual 6v coils.

I have control boards I can photo for you as well as original manuals but again, non of them cover a 32v DC section...

Good luck and I hope you get her working. I got me a soft spot for the W and V-45 series :D

Maybe this should be moved to the Onan forum??? Might get more attention...
 

RodneyBates

Subscriber
Last Subscription Date
07/09/2019
Thanks Angry Sailor. After checking the plate does say 36 volts output, but does also say use 32 volt battery. I will try to attach photos. Sorry, computer problem, I will send as soon as I can.
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
Polarity should be able to be changed merely by electrically cranking the set with the desired polarity. The residual magnetism will then be reversed, and it will always build up with the new polarity, even when hand cranked.

I would GUESS that, to crank electrically, the battery is connected between ground and S1. This must be disconnected when the emgine starts.

I'm not as familiar with Onan's, but all of my Kohlers have magnetos, allowing them to be started without a battery if necessary. Probably was an option for the Onans too...

Keith
 

John Newman Jr.

Subscriber
Age
64
Last Subscription Date
12/23/2019
While I have never seen a 32VDC model, They are shown in the manual. But the wiring diagram led me to believe that they were either 115VAC or 32VDC. Not both. Please post a picture of the ID tag if you can.
I’m not home to look at the book right now, but I’ll check when I get back.
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Interesting, I’ve never seen one like that... I’ll have to look at my manuals again see if it’s in there. Could swear it isn’t, but I’ll look tomorrow.
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
I have heard of sets where small loads, such a few lights, can be supplied by the battery without having to run the engine. The battery is then recharged anytime the set is running, such as while supplying AC loads.

Keith
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Makes perfect sense, just don’t recall ever seeing that W3S-105M designation or a 32v W series. Very cool and I’d guess somewhat rare/odd ball

If I remember right the letter suffix is M for magneto, S for electric start and A for automatic (load demand) start.

Also have never seen a 2250w AC section. Most are 3000w and the earlier ones were 2000w. I’m pretty sure the 2000w W series were very early models and can be identified by having a 2 3/4” bore as opposed to the 3” bore... memory is a bit foggy on this so may be wrong, but I seem to remember this was the case.

Are you sure that positive wire goes to ground? There is an insulating grommet on the positive stud. Chassis is negative.
 

Power

Registered
Except for the missing relay panel, looks unmolested. At some point, someone cared enough to fit hardware cloth around generator vents to keep rodents out.

No pix of top of radiator- do you have the unobtanium radiator cap?
If you add up the AC and DC watts, get 3000, so you probably have the 3 inch bore engine.
Might want to look around wherever set came from for the board. I do not know where you would get 36 volt reverse current and starting relays. There will not be much on the board- Starting relay, reverse current relay, charging resistors, probably a terminal strip for remote start & stop.

Both the stop button, and the high water temp switch ground out the magneto points. The start button energizes a starter relay that connects generator windings to the batteries.

If it was mine,I would see if it will start with 24 volts (2- 12 volt batteries) If it does, many large trucks use 2- 12 volt batteries for 24 volts, as do all military vehicles and military generators. 24 volt parts are available at truck repair facilities and as military surplus. The MEP series military generators probably came with the parts you need.
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Good call about the total watts.

What about using 3x12v batteries, a modern 24v solenoid with the control side tapped onto two of the batteries and an big azz diode for the reverse current? Wouldn’t be original but could work. This would let the set charge at 32-36v. I bet an original start relay would work also (12v control). The high current side is a big azz brush contact which I don’t think would be bothered by 32v...
 

RodneyBates

Subscriber
Last Subscription Date
07/09/2019
Well, I just fired it up and checked for the umpteenth time, and yes, the positive is to ground. Could be that someone in the past has reversed the polarity as Vanman has suggested? How much can I mess up if I try reversing it? Sorry to ask such a question, but I am a novice on generators. The large white wire in the control box is connected to the insulated post, and the uninsulated post is grounded to chassis. The large black wire goes to the 115 outlet as does the smaller wire grounded to chassis.

Power: I will be posting a pic of the radiator cap - is this one of the "unobtanium"? Have to post it from my phone, as my computer says it has no space in the C drive!
 

Power

Registered
Good call about the total watts.

What about using 3x12v batteries, a modern 24v solenoid with the control side tapped onto two of the batteries and an big azz diode for the reverse current? Wouldn’t be original but could work. This would let the set charge at 32-36v. I bet an original start relay would work also (12v control). The high current side is a big azz brush contact which I don’t think would be bothered by 32v...
Yeah, I thought about 3-12's, but charging voltage is around 2.35 volts per cell = 42+ volts ( add 1/2 volt or so for diode & wiring) for 3 batteries. That seemed a bit much for an old set rated at 36 volts. If set will crank, seems easier to use standard 24 volt parts and drop 36 volts to 28 for batteries.
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
That is IT. RARE as unicorn turds. :crazy:

As for reversing the polarity, I THINK Vanman is correct, I’m not raised on DC, but I wonder if the brush timing would need to be reset :shrug:

Maybe one of the smarter guys can explain better.
Edit: maybe someone smarter (or less tired) than the guy who calculated 3x12=32 in his head...:bonk:

In my defence, I’ve been shuffled around airports all day making my way home. ETA is 4am Atlantic. Ways to go yet:(
 

Tim B

Subscriber
Last Subscription Date
04/22/2020
My W2C book shows a wiring diagram for a "Dual Purpose Pant" with magneto, 32volt battery and either a 115VAC or 230VAC. Negative ground also.
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
My W2C book shows a wiring diagram for a "Dual Purpose Pant" with magneto, 32volt battery and either a 115VAC or 230VAC. Negative ground also.
I’m really interested to check my book now. I don’t recall seeing that... I’ll check tomorrow. Could you post a photo of the page?
 

Kevin K

Subscriber
Last Subscription Date
07/12/2019
I see that they did have a 32 volt unit, negative ground. From your picture it looks like someone has done some rewiring in the generator head to make it positive ground. The heavy tan wire in the control box should be positive, instead it is grounded and there is a heavy black wire coming from the generator section and exiting through a hole.
 

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