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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 6.5 NHD-FB/1M repair or sell?


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  #1  
Old 11-09-2017, 08:29:11 PM
RadicalDad RadicalDad is offline
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Default Onan 6.5 NHD-FB/1M repair or sell?

I inherited an Onan 6.5 NHD-FB/1M as part of the house I currently own. It is used as a backup generator, so it has low hours - under 1100 (not going outside to check exactly at the moment). It runs on natural gas and seems to have an OEM natural gas conversion kit installed. It is installed on a concrete pad and has noise cover which somewhat protects it from the elements. Since I've lived here, we have blackouts about 3x per winter, usually no more than 10 hours each. How it got to 1100 hours, when by that math a 19 year old generator should have about 600 hours, is beyond me.

We have it professionally serviced annually, and I run it once a month or so to keep the slip rings in good shape. The previous homeowner told me to do that, so I assume he did that also.

Currently the generator has frequent Hz spikes. It runs about 62 Hz, but will momentarily spike to 90 - 120 Hz. It will run fine for 10 minutes or so, then go through a couple of minutes of spikes every 2 seconds to 15 seconds, then calm down again. When this happens there are no significant changes to the load (the furnace or refrigerator hasn't turned on or off), nor is there an audible change in the speed or workload on the genset engine. It seems to behave better under heavier load, but even then the spikes still occur, just less often. I'm assuming the problem is the voltage regulator, but if someone knows better, I'm all ears.

These spikes are playing havoc with electronics in the house. I'm already on the 3rd logic board for a 6-year-old furnace, so I can't let this ride.

Cummins NW doesn't want to service the generator any more, and they won't fix it because an OEM voltage regulator isn't available and they won't install aftermarket parts. I've found someone else who will repair and service it, but the estimated price of annual maintenance plus repair labor plus a voltage regulator from Flight Systems is about $900.

Thus I'm thinking to sell this one and get a new generator I can service myself. (Oil changes and spark plug replacement are about my speed - servicing the slip rings is beyond my knowledge base.) With such low hours, I figure there is someone out there who would love to have this thing and service it themselves.

What might it be worth to sell, and where would I advertise it? https://www.enginads.com/classifieds/showcat.php/cat/14
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Old 11-09-2017, 08:30:45 PM
len k len k is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

First of all I don't think jumping from 60 to 90 hertz is real, if it did happen you would hear the engine rev up ( that's a 50 % increase in rpm) I suspect it's a quirk of how your hz meter is meauring hz. Most people here use a kill-a-watt meter to measure hz.

Even ~ 1000 hours is low, read one CL ad that said one would need a rebuild as it had 8700 hours on it, but still ran.

I'ld check that brushes are not worn, broke or sticking in their holders.
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Old 11-09-2017, 08:33:43 PM
len k len k is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

Not really much to maintain, other than change oil and filter occasionally, easy to DIY.
Do want to run gen once a month to lube engine and self clean slip rings.

To sell Craigs list is convient, might get more on Ebay.

First of all I don't think jumping from 60 to 90 hertz is real, if it did happen you would hear the engine rev up ( that's a 50 % increase in rpm) I suspect it's a quirk of how your hz meter is meauring hz. Most people here use a kill-a-watt meter to measure hz. If high HZ are real , it's likely the gov electronics modual, can send to Flight Systems to test it. New one from FS is ~ $190 I think.

Voltage should be stable as it has an electronic AC voltage reg.

Even ~ 1000 hours is low, read one CL ad that said one would need a rebuild as it had 8700 hours on it, but still ran.

I'ld check that brushes are not worn, broke or sticking in their holders.

For AC voltage reg ( VR1) we recomend Flight Systems. They sell very reliable aftermarket AC voltage regs at a good price, plus they have 2 year warentee. They recently started selling replacement electronic govs moduals too, if you need it.

Manual and link to them
BGD-NHD begin Spec H --110-220V SERVICE --(11-95)-- 965-0500.pdf
BGD-BGDL_PARTS_Spec_A-M -- (7-98)--965-0228.pdf
http://www.twinslan.net/~n0nas/manuals/onan/

Last edited by len k; 11-09-2017 at 08:44:52 PM.
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Old 11-09-2017, 08:44:57 PM
RadicalDad RadicalDad is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

[Quote below from a doubled post - I'm copying it here as I've asked the mods to delete the other one]

Quote:
Originally Posted by len k View Post
First of all I don't think jumping from 60 to 90 hertz is real, if it did happen you would hear the engine rev up ( that's a 50 % increase in rpm) I suspect it's a quirk of how your hz meter is meauring hz. Most people here use a kill-a-watt meter to measure hz.

Even ~ 1000 hours is low, read one CL ad that said one would need a rebuild as it had 8700 hours on it, but still ran.

I'd check that brushes are not worn, broke or sticking in their holders.
I have much of my equipment on battery backups. The observed Hz spikes exactly correspond to the battery backups shifting to battery power. The Hz spikes are real. The battery backups are doing their job - shifting to battery when the line power goes out of spec.

I don't have the ability to check the brushes, and Cummins NW has been obnoxious about doing that work, even though they were specifically asked to do so, having observed this problem prior to my last annual maintenance. That is why I'm thinking to sell this thing.
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Old 11-09-2017, 08:48:51 PM
len k len k is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

Might want to find a good independent gen man, I've heard Cummins doesn't have good techs anymore. And are more interested in selling anew gen than repairs, more profit.

Some backups are too fussy about wanting a tight range of voltage & Hz or they will trip.

If you just don't have the info to repair your gen , I've included a link to service manual for your gen. It explains things pretty well, It's not rocket science.

By-the way I have a gen very similar to yours, a 7NHM
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Old 11-09-2017, 09:31:38 PM
Newoldstock Newoldstock is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

A low hour stationary plant in an encloser with an NG kit.
That is what most people want in the first place.

Oil changes and spark plugs on that unit are already as easy as they come.
Your Onan even has a nice plastic cover that pops off for easy access to the brushes and rings for service.
People are scared of the electrical end of things and brush service.
You can learn...
Nothing here is harder as working on a car from the 80s.

As far as your frequency spike is concerned I think your instrumentation is at fault not your machine.
Get one of these tiny tach type hour meters and you can see exactly how fast the engine is turning and track your hours for your own service.
http://www.chappellsupply.com/produc...r-32-0416/481/
( these work great I have spun them up to 7000 rpm and they are accurate and reliable and don't shake apart ).

If your furnace is blowing up boards it might be a furnace problem.
They don't make furnaces like they use to and they don't make generators like they used to.

I had a fellow come service my furnace and he changed a lot of parts.
I was angered by this because I had already trouble shot the unit and knew what was wrong, I even told them on the phone what parts to bring.
I do not have a TSSA number so I can not buy furnace parts ( unless I go online and want to wait a couple of weeks ).
We had a loud and unpleasant discussion about the parts swapping and piss poor trouble shooting methods they used...

Very often I find the service people are selling you parts that may not be the best parts for you.
They know this, but your not going to do anything about it because you can't fix your own furnace these days.
My advice is find a furnace guy that knows your unit and will apply a fix that sticks like an upgraded aftermarket igniter control ( if that is your problem ).
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Old 11-09-2017, 10:03:24 PM
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BigBlockChev BigBlockChev is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

Another thing to check is that all your connections are tight in your breaker boxes and panels. A loose connection can create havoc with electronics. I had a customer who burned out a lot of electronic gizmos to the tune of several hundred dollars , turned out he had a couple of loose screws on his breakers , it even burnt back the insulation on one of his large diameter feed wires. As len K said the Hz change might not be actual just electrical noise. If the sound from the engine isn't changing when this happens then the HZ are not changing as they are dependent on engine speed only. Generally with a large change in engine speed you will get hella voltage spikes even with the voltage regulator trying to compensate. My gut says loose connection causing arcing somewhere, maybe others can chime in. A scan with a thermal camera of your breaker panels and junction boxes can indicate this very quickly. Cheers Dan
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Old 11-09-2017, 11:57:36 PM
len k len k is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

Check your neutral connection. With a bad or open neutral , the votlages on the hots will seasaw in a voltage divider fashion as loads change.

I assume your not backfeeing thur a electric dryier plug. Not only is it danagerous , some don't have a neutral.
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Old 11-10-2017, 10:09:33 AM
Newoldstock Newoldstock is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

If it is a wiring issue in the home you will notice other things.
Do lighting load get dimmer and brighter when the wash machine of a hair drier is used in different parts of the house?
Do you have problems with other electronics around the home?
If non of this checks out it could be a wiring problem on the neutral side of your transfer switch from the generator.

If it is not the generator or the utility side inside your home connections, it could be the utility power and your generator is fine.
Some places have really awful power or problems on the utility side of the service ( a bad ground or loose connection ).
If it is a supply side issue it will not cost you anything to fix, but you will have to convince them o come and look for it.

If your a scavenger like me keep an eye out for a ferroreosonant transformer.
These are power conditioners that will eat up any voltage spike and protect the equipment they feed.
People like little UPS with batteries and cheap voltage suppressors not big heavy things they do not understand so these get tossed in the scrap a lot.
This requires no batteries, service or inspections and will protect electronics from spikes and surges ( there are many different brands )
http://www.a1parts.ca/transformers/H..._CV_Series.htm
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Old 11-10-2017, 10:32:06 AM
akirkland akirkland is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

There are other generator companies in the Portland area besides Cummins.
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Old 11-10-2017, 11:17:13 AM
Pete Spaco Pete Spaco is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

"Currently the generator has frequent Hz spikes. It runs about 62 Hz, but will momentarily spike to 90 - 120 Hz. It will run fine for 10 minutes or so, then go through a couple of minutes of spikes every 2 seconds to 15 seconds, then calm down again. When this happens there are no significant changes to the load (the furnace or refrigerator hasn't turned on or off), nor is there an audible change in the speed or workload on the genset engine. It seems to behave better under heavier load, but even then the spikes still occur, just less often. I'm assuming the problem is the voltage regulator, but if someone knows better, I'm all ears."

As previously mentioned, this generator CAN NOT create increase frequency unless the engine speed increases.
Do you know whether this is happening when the spikes occur, or not?


Tell us how you measure those "frequency spikes".

"I have much of my equipment on battery backups. The observed Hz spikes exactly correspond to the battery backups shifting to battery power. The Hz spikes are real. The battery backups are doing their job - shifting to battery when the line power goes out of spec."
Are you certain that the frequency spikes are coming from the generator and not from the "battery power" equipment? You could be suffering from a power DROP OUT from the generator.
If you disable the battery backup, do the "frequency spikes" still occur?

Pete Stanaitis
---------------
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Old 11-10-2017, 08:32:00 PM
RadicalDad RadicalDad is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

Quote:
As previously mentioned, this generator CAN NOT create increase frequency unless the engine speed increases.
Do you know whether this is happening when the spikes occur, or not?
The Hz spikes are too fast and too frequent to be correlated with changes in engine speed. And I don't hear anything different in the genset when these occur.

Quote:
Are you certain that the frequency spikes are coming from the generator and not from the "battery power" equipment? You could be suffering from a power DROP OUT from the generator.
If you disable the battery backup, do the "frequency spikes" still occur?
I am measuring direct from the wall socket, not the battery backup outlets. True, I'm using cheap multitesting meters, but two of them are reporting the same thing. Again, for clarity, when the battery backup relays click, that is when I see momentary Hz spikes. Setting one cheap meter to look at voltage, and the other to look at Hz, I don't see voltage spikes, only Hz spikes. And also to repeat, both meters show Hz spikes. Hard to imagine that two different meter brands of completely different design would show the same problem. And the problem doesn't occur on utility power, only on generator power.

Other folks in this thread have suggested possible faults in the wiring at various places in the house, the electrical panel, and out to the generator. Many thanks for those suggestions. Unfortunately, I had an electrician in last spring to investigate those possibilities. He went through the entire electrical box and the runs from it looking for loose connections and other faults. Found a few problems, but nothing that would account for what we're seeing. He even put in a new circuit that has just one outlet next to the box that we used for testing. It shows the same problems, even when that circuit is the only one connected to the generator.

As for my learning to do the maintenance - well maybe. I'm currently earning my third graduate degree and I work as clergy. Which is to say, I have to be careful about what I take on - there is only so much time in a day. Despite the fact that my first career was in software engineering, it seems I ought to be able to pay to have this maintenance done and stick to doing the things I'm good at that no one else can do. My poor experience with Cummins NW and inability to find someone else who isn't flakey to service this generator is why I'm considering selling it to someone who can love it while I get something that will support my needs.

Speaking of being clergy, there is a big life-cycle event happening this weekend. I've been prepping with the family and fellow clergy all day and I've got visiting clergy house guests tonight through the weekend. Which is to say, thanks for everyone's ideas, please keep them coming, apologies for my delay in replying today, and I won't be able to look at the forum again until late Sunday. Everyone here have a sweet weekend!
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Old 11-10-2017, 09:04:24 PM
len k len k is offline
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Default Re: Onan 6.5 NHD-FB/1M repair or sell?

I wouldn't sell it, I think if you do you'll be longing to get it back. Think you'll be even more disappointed with what they are selling new these days.

HZ are DIRECTLY porpotional to engine RPM, so bottom line if engine RPM is not increasing by 50 % then 50% increase of 60 hz to 90HZ is NOT real ( not really occurring). I seriously doubt gen is suddenly turning at 90hz.

Tell me about these breif 90 hz times. Do they instantly occur or ramp up over several to 10 or more seconds. When they occur does the carb throttle suddenly increase?

I wouldn't use your charger/inverter tripping out as evidence that hz are high, use a hz meter. Charger/inverters have a history of trip points being set too tight, and even tripping out on an Onan 7.5JB gen with a massive flywheel ( it can't change rpm that fast). Most people here use a $25 kill-a-watt meter ( home depot or ebay) with good results to measure HZ.

If brushes or AC voltage reg are intermittent that might create an interrupted sine wave that some cheap hz meters might interpret as a higher than 60 hz output, even though gen is still turning at equivalent of 60 hz (1800 rpm). ( meters use differentl methods to measure hz, some methods are more susceptible to errors)


I suspect your hz meter is being fooled and 90 hz is not real.

This is not a big project. As I already said I'ld check that brushes are not sticking, broke , or worn. Service manual tells you where they are and how to measure them. Down load the service manual (965-0500) I listed in post 3, and look at paper page 51 for how to measure brush wear. They are easy to get at.

Last edited by len k; 11-10-2017 at 09:37:46 PM.
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