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Onan Emerald 4000 BGE help!


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  #1  
Old 06-25-2017, 01:18:15 AM
bigGURN bigGURN is offline
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Default Onan Emerald 4000 BGE help!

Picked up this onan for $100... was told it did run when pulled from camper... now not so much. Here is the tag:


So.... it'll run as long as I hold the start button down... let go, and it dies.

It'll stay running if I jump 12v to the coil, runs and sounds great!. Dies when I cut the 12v off.

The one issue I can find is no 120v out put... brushes look fine, the slip rings test with in spec (27ohms if memory serves is what I got)...

Could this be a board issue or should I look else where? I'm not an electronics repair guy, but need to get this up amd running as we want to use it with the new camper. Thanks in advance!
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Old 06-25-2017, 07:09:32 AM
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Default Re: Onan Emerald 4000 BGE help!

Ahhhh.... the old "it ran when it was removed" story. Still, for $100 you did good. If the generator is not producing power it will not continue to run when you release the start switch. The most likely suspect is a bad voltage regulator, about $250.

Get the service manuals here: http://www.twinslan.net/~n0nas/manuals/onan/

965-0528 Service
965-0231 Parts
965-0628 Install
965-0128 Operator

Go to page 7-7 and follow the flow chart for "engine starts but stops when start switch released".

Make sure the slip rings are clean.
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Old 06-25-2017, 09:40:16 AM
bigGURN bigGURN is offline
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Default Re: Onan Emerald 4000 BGE help!

Thanks. Going over that list, looks like the VR is the next and only item yet to be tested. So, I'll start there this afternoon and report back.
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Old 06-25-2017, 10:49:32 AM
Gunny Gunny is offline
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Default Re: Onan Emerald 4000 BGE help!

Do he tests in the trouble shooting tree. If you determine it is the VR, I'd recommend getting a new one from Flight Systems. A better product at a better price with a better warranty and good tech support when compared to OEM.
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Old 06-25-2017, 10:52:20 AM
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Default Re: Onan Emerald 4000 BGE help!

Was looking at their products last night. Figured I'll go that route. If the VR is bad, I'll order it from them. May go ahead and replace the board too. Mine has been soldred on at some point, so for an extra $140, I may just add that to the parts list. I'll test the VR this afternoon and see what I determine.
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Old 06-25-2017, 11:29:04 AM
len k len k is offline
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Default Re: Onan Emerald 4000 BGE help!

27 sounds good if you measured it thru the brushes and with AC voltage reg unplugged. Also with reg unplugged measure from slip ring to frame should be > ~ 1,000,000 ohms ( insulation test).

To test stator with AC reg unplugged apply 12 VDC across brushes, when running stator should make :
~ 40-50 VAC out the T windings
~55-60 out the Q windings
something like ~ 7 out the B windings.

Also check that control board applies ~ 9-12 VDC to pin 7 of AC reg while starting. (flashing)

OF course check brushes for sticking ,wear, breaks.
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Old 06-25-2017, 11:30:29 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan Emerald 4000 BGE help!

I have used Flight Systems for over thirty years. Good people to deal with know what they are talking about. Build a better product than OEM. I have never had a problem with them. I sent in a board for repair one Monday morning. Had it back that Friday.
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Old 06-25-2017, 03:58:36 PM
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Default Re: Onan Emerald 4000 BGE help!

Just went through the VR test and sure enough, it failed on the last set, terminals 5-3 came back open. So that answers that! I'll go ahead and replace the board and brushes as the board has issues and the slip rings are quite dirty. I see that Flight Systems offers a quick tool for cleaning the slip rings, so I'll add one of those to the list. Thanks for all the help!
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Old 06-25-2017, 04:36:30 PM
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Default Re: Onan Emerald 4000 BGE help!

That tool they have is a brush stone. Very easy to break. Just let it ride on the ring. Doesn't take much pressure.
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Old 07-06-2017, 06:54:33 PM
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Default Re: Onan Emerald 4000 BGE help!

Cleaned slip rings, new brushes, a regulator and board from flight systems and away she goes!
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Old 07-06-2017, 09:01:26 PM
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Default Re: Onan Emerald 4000 BGE help!

It sounds pretty good but sounds like rpm is high. Should be 1860 no load.
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Old 07-06-2017, 09:06:40 PM
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Default Re: Onan Emerald 4000 BGE help!

It currently has no exhaust. It sounds fast, but it could be that. I'll check it though once the exhaust is mounted.
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Old 07-15-2017, 10:30:42 PM
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Default Re: Onan Emerald 4000 BGE help!

All together on a cart and ready to go. With the exhaust it is so much quieter. Checked the output and it was spot on, so looks like the engine speed is correct.


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Old 07-15-2017, 11:03:54 PM
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Default Re: Onan Emerald 4000 BGE help!

I'm liking the fuel cell in the first video.
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Old 07-15-2017, 11:05:24 PM
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Default Re: Onan Emerald 4000 BGE help!

necessity... the mother of all invention?
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Old 07-16-2017, 02:08:36 PM
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Default Re: Onan Emerald 4000 BGE help!

I think with the electronic voltage regulator, proper voltage output is NOT dependent upon speed. Check speed with a Kill-A-Watt device or other frequency-measuring device. Still could be running too fast, with proper output voltage.
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Old 07-16-2017, 02:23:40 PM
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Default Re: Onan Emerald 4000 BGE help!

If it had 8 inch transformer (voltage booster) by starter (spec A-C) then voltage is proportional to speed.

You have electronic voltage reg. So voltage is independent of speed, unless hz is real low, like 50 hz. Then some aftermarket electronic voltage regs reduce voltage to try to help a heavily loaded engine come back up to speed
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Old 07-20-2017, 11:01:39 PM
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Default Re: Onan Emerald 4000 BGE help!

She's ready to go! Decided to go mobile with it. Really has been a fun side project, and I learned a lot, which is something that I love to do! I was even able to use some of what I learned to repair our old Toro T500 Generator that had some filthy slip rings! Thanks so much for all of the input and assistance provided here!
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Old 08-09-2017, 01:56:18 PM
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Default Re: Onan Emerald 4000 BGE help!

So... everything works great... except I am not charging the battery. Is there a separate regulator for 12v?
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Old 08-09-2017, 02:33:00 PM
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Default Re: Onan Emerald 4000 BGE help!

There should be a battery charge winding in the generator. The BGE's sold for motor homes had a rudimentary charging system consisting of a bridge rectifier and a resistor. It wasn't even really a charging system, more like something to keep the battery from discharging with the generator running. The battery charge function was provided by the battery maintainer in the coach. The BGD's sold for industrial or bucket truck use usually had a regulator/rectifier to take care of battery charging.

If you provide a full model number maybe we can pull up a wiring diagram.
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