Onan Emerald 3 - Worth putting a new main seal in?

elib

Sponsor
I have the offer of an Emerald 3 that was taken out of service because it needed the main seal replaced a second time. I could have it for free. It's been sitting for 10+ years under a tarp and doesn't look to have any nests in it. It was only ever used with LPG.

Does this have the makings of a decent project or should I just let it go to the scrap yard? The plate appears to say it's 120v only, is that true? 240v is more useful to run my well pump but 120v wouldn't be terrible. The model number doesn't seem to be readable unless it's a 100d?

Is leaking oil most likely to be from a bad main seal on this model or could they be mistaken? Is it a difficult job to replace? I'm handy and not afraid to undertake the task.

Thanks in advance!
 

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YellowLister

Subscriber
I would grab it for free.. parts are parts.. but before you fix the seal, or attempt to start it, clean the slip rings so you dont zap the voltage regulator..

Some of those are transformer regulated but most have a board that will go bad if it's been sitting and there is resistance between the slip rings and brushes so clean them first..

Then get it to run if it makes power they are pretty good sets, but the v.r board is 200 to 300 bucks to replace.

Fixing the rear main seal is a whole other bag of worms.. and if you dont take it apart right you can damage the generator end..
 

elib

Sponsor
Thanks for the info guys. I'll bring it home, blow out all the cobwebs and clean the slip rings and check the breather/PVC. Apparently they replaced the seal one time before and didn't want to do a second time so they replaced. At the very least the LPG conversion kit on it is worth scoring to adapt a different motor later.
 

slip knot

Subscriber
If you decide to scrap it I may be interested in the LPG parts on it. I've got one I would like to run on propane.
 

Vanman

Subscriber
If the overpriced original AVR is faulty, couldn't it be replaced with the cheap SX-460? And keep a couple of spares on hand?
 

len k

Subscriber
Possibly, have to check on the amp supply specs of sx-460. I considered that in past, but didn;t get around to looking.
 

elib

Sponsor
Wow I had no idea. If I can restrap it to 240 that would be amazing. Now I'm getting excited. I tried to pick this thing up today, oof. I'm going back with a hand truck/dolly and possibly another set of hands to help me.

Being a Emerald 3 I'm guessing it's a newer version so likely has the electronic AC votlage reg, ( instead of ~ 8 inch current transformer by the starter)

Can convert to 120/220 if they brought all 4 leads out of the stator windings. Read this link

https://www.smokstak.com/forum/showthread.php?t=154516
 

elib

Sponsor
If you decide to scrap it I may be interested in the LPG parts on it. I've got one I would like to run on propane.
I will keep it in mind but if this doesn't work out I plan on trying the LPG parts on something else. Probably won't want to sell them.
 

elib

Sponsor
I attached a picture of the starter end, is the large green box under the solenoid the transformer?

Being a Emerald 3 I'm guessing it's a newer version so likely has the electronic AC votlage reg, ( instead of ~ 8 inch current transformer by the starter)

Can convert to 120/220 if they brought all 4 leads out of the stator windings. Read this link

https://www.smokstak.com/forum/showthread.php?t=154516
 

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Kevin K

Subscriber
From what little I can read on the label, it looks like a 6.5NHE spec D with a date code of G88, July 1988. It has points and an electronic voltage regulator. I wish someone would offer me one for free, even if I need to replace the rear seal.
 

Motorhead

Subscriber
I attached a picture of the starter end, is the large green box under the solenoid the transformer?
Oh LORD, The WORST way to store something is on dirt with a tarp over it. Turns it into a lump of rust and aluminum dust quick!
That set has it's own battery charging system, I believe, seeing the resistor on the side. It is an early set with points.

I would figure out FIRST if it runs and how much blow by it might have. Try to port into the engine pressurized oil and see if the oil pressure is too high from a stuck oil pressure relief and having the rear seal leak from too high of oil pressure.

Sitting for 10 years, I'd suggest pulling the heads before you try to start it. Squirt some KROIL or other penetrant in the cylinders, one at a time with the cylinder pointing UP. The penetrant will soak and loosen any stuck rings, hopefully.

I have a propane vapor, 4BGE in my 5th wheel and it is a great little set, if you properly maintain it.
 

len k

Subscriber
The gen in post 11 does NOT look like it has the current transformer, Tranformer is LARGE. ~ 8x8x8 inch cube at least.

So that means it has an electronic reg, the reg is likely inside the control box, that holds the start/stop switch.

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Sitting on ground is not a good place to store a gen. Mice can also build a nest inside and nest can break off plastic ignition trigger arm. It's located between engine and genhead.

BEfore you crank engine , Might want to remove ignition modual from top of engine and look down hole to see if there is any nest you can fish out. Also same from cooling fins on front and back sides. MAybe even remove starter to look and fish out any nest.

If plastic arms break you'll have to remove genhead from engine to get at it, not a small job.
 

Motorhead

Subscriber
Len, I think that is a points engine? It has the cover on top with a bail to hold it.

But very good advice to the OP a bout mice (The little Ba$t@rds)
 

len k

Subscriber
Your right ... points, that's good. I just looked in NHE parts manual. Electronic ignition didn't start till spec G , this one looks like it's spec D. I keep thinking Emerald III is newer spec numbers.

Manual numbers and link to them
BGE spec f-k---NHE-spec e-k--EMERALD PLUS--SERVICE--(9-94)--- 965-0528
NHE-NHEL spec d-p EMERALD III---PARTS manual---940-0228
https://www.twinslan.net/~n0nas/manuals/onan/

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I store my 7NHN outside ~ 2ft up on plywood & cement blocks under a tarp, (plastic air mattress). Was cleaning things and left a roll of toilet paper (TP) next to gen. Came back in a month and looked, shreds of TP all around. SO I looked inside and fished them all out before starting it. Also found it blocking cooling fins. Don't leave rolls of TP around a gen, it's nesting materiel. Not easy to see in there or fish it out either.

I plan on building a box to hold gen, with ~ 1/4 inch mesh over bottom cooling air vents to keep mice out, whole thing up 2 feet off ground to keep it out of rain splash zone and allow cooling air to flow in/out underside.

My gen sitting outside https://www.smokstak.com/forum/attachment.php?attachmentid=321842&d=1540935225
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elib

Sponsor
Dirt definately is not the place. This is actually on a concrete slab but the forest detrius has been allowed to accumulate for a few years. Good advice re: rodents, I'll give it a good clean before doing anything else. Glad to hear it's got electronic reg.


The gen in post 11 does NOT look like it has the current transformer, Tranformer is LARGE. ~ 8x8x8 inch cube at least.

So that means it has an electronic reg, the reg is likely inside the control box, that holds the start/stop switch.

-----------------------------

Sitting on ground is not a good place to store a gen. Mice can also build a nest inside and nest can break off plastic ignition trigger arm. It's located between engine and genhead.

BEfore you crank engine , Might want to remove ignition modual from top of engine and look down hole to see if there is any nest you can fish out. Also same from cooling fins on front and back sides. MAybe even remove starter to look and fish out any nest.

If plastic arms break you'll have to remove genhead from engine to get at it, not a small job.
 

len k

Subscriber
Having an electronic AC voltage reg is a plus if you want to convert gen from 120 only to 120/240 output.

AC electronic reg does have an issue. IF gen sits for months slip rings develop a clear coating that makes high contact resistance to brushes. That can stress and kill reg when you start making AC. SO if it's been sitting , clean slip rings with schotch brite pad before making AC.

I've let mine sit outside under tarp ~ 6 months and I got ~ 100 ohms between brushes ( rotor is ~ 25 ohms) people with dead regs have reported 300-700 ohms. Don't know that threshold to kill reg is .
 

len k

Subscriber
If the overpriced original AVR is faulty, couldn't it be replaced with the cheap SX-460? And keep a couple of spares on hand?
Rotor ohms on electronic reg Emeralds are 20.25 - 24.75 ohms, IIRC Onan manual says voltage to rotor is ~18-60 VDC, so that's ~ 3.0 amps max. Have to look if sx460 can supply that.

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some sx460 Info--> https://www.americasgenerators.com/uploads/docs/NEWAGE SX 460 Automatic Voltage Regulator.pdf

Looks like SX460 can supply 4 amp max (6 amp for 10sec), 90VDC ( with 207V input), and needs min rotor resistance of 15 ohms..... so seems MIGHT be ok. Have to find and check specs to see if can get 60VDC out with 120VAC input to reg.


Might have to use auto flashing ( control board wire to pin 7 of Onan reg, and a series diode). SX 460 specs elude to 3.5 -4 VAC at reg terminals for "build up voltage". I ASSUME that's what reg needs to start bootstraping it's way to 120V output. IIRC without flashing, stator only makes 1-2 VAC

Simple solution is try it and see if it works.

Otherwise have to look at which terminal sx460 uses for rotor ground , and maybe set up a flashing drive ( 12VDC) into other rotor terminal, using a diode in series with 12V source so reg power can't flow backwards into 12V line. Typical for AC and DC grounds to be same point, the frame( at least in Onan 's design). Would be good to find and look at internal schematic for a sx460 to check on that.


I'm getting lazy in my old age. Think I'll just order aftermarket reg from Flight Systems. ~ $240 instead of ~ $600:bonk: from Onan. Drop in replacement, same form , fit and function.
No checking schematics and testing...... it got COLD and WINDY!!!!!!! early this year.... 15 degs last night. Garage is full, gen is outside.

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