Replacing a built-in Onan generator in a Class-A

[Ped]

Onans have a bunch of ignition kill safety switches. Most generators have only oil level. These even have voltage regulator and stator out put fail switches. Plus they have fuel pumps and fuel filters to look at.

So first thing is to get one of these https://www.harborfreight.com/90-in...43BTg65yY_aQ9OfX_RqOi1OE9Cv70hSBoCqmIQAvD_BwE

If youre getting spark need to test fuel pump/filter. Take bowl drain out and see if gas comes out. If so check spark plug to see if its wet from gas. If not clean carb jets.

If youre not getting spark check oil level. Also turn breaker to transfer switch off. Its located at the generators outside panel usually. If it runs after turning power off let it warm up completely then flip the breaker. If it keeps dying its a voltage regulator or idle or air/fuel mixture not spinning the engine at the right RPM. You can check RPM with a tool. If it keeps going omce its warms its probably lean.

 

[Supervstech]

The genny is LP not gasoline... no filters, pumps or the like...

 

[Ped]

Well that rules out most the fuel side except mixture. So now you can focus on spark. Again start with oil level.

 

[JeepHammer]

The earlier Onan engines were set up for diesel/propane or gasoline/propane.
Hardened valve seats, stainless valves, ect.

The engines can be rebuilt by any engine shop for a very reasonable price.
The engine is small enough to roll around on the bench, so they are stupid easy to rebuild,
They are cast iron, so live virtually forever.
Even if the cylinder walls is gouged, it's cost effective to bore and insert a sleeve to restore cylinder walls.

I sucked up rebuild kits and a factory propane kit off the surplus market, these engines were used everywhere and there are piles of parts on the surplus market.
Get a manual and parts list for your model, then order a copy of superceded parts with the updated part numbers, you will be surprised how many parts interchange.

ANY electric motor or welder rebuild shop can fix the generator end.
Keep in mind these things are built to be rebuilt, the old Onan generator is 'Open' wound, most times all the rotor/stator need is dipped in insulating material again, contacts cleaned and brushes replaced.

Keep in mind this is what I did for a living for several years...
The red 'Paint' is an electrical insulator, and the most common brand is 'Glyptal',
Shafts are protected from the paint and dipped many times, and when you start watching the INDUSTRIAL built units, you will find it used everywhere...

Notice even the Electrical Current Rectifier has been coated in paint on this alternator.
This stuff not only electrically insulates, it stops corrosion, sets up solid so the windings don't get battered around, and it resists/repels rodents.
You don't find it much on 'Consumer' products, but industrial applications love it and coat everything in it.

 

[JeepHammer]

You can also get some fine bird screen mesh and seal off the generator from rodents and still allow airflow -Let's face it, every generator is susceptible to rodents, step 1 is to keep them out.

View attachment 338

Exactly.
I rebuilt these things for years, and it's 99% user error, failure of coach builder to prep the unit for the application.
Rodent screens and storage prep kits are available... The coach builders simply didn't use them.

The unit is Industrial, it's intended to run more than it's shut down, and rodents don't enter an often used generator.
End user is *Supposed* to prep the unit for the application, keep it out of the rain, keep rodents away from it or prep the unit for rodents, long term storage/disuse, etc.

There are few places rodents can get into the genset, and wire screen keeps them out.
Might as well call it 'Step 1, and Done.'

The control/connection box is where I see most damage, people leave knockout holes open and the control/ignition wiring wide open to rodents.
The good news it's easy to fix/replace that wiring.
When you need to strip/re-insulate the rotor or stator, that's a heavy job that involves dipping the parts in solvent and insulation material.

*IF* the unit needs re-wound, you CAN do that by hand, most units are hand wound in small shops.
The lacquer or epoxy insulated wire isn't too expensive, and when ordered soft it's easy to shape.

If you are afraid of mechanical work, go to a shop and trade dollars for work.

A simple wire cage around generator end vents and plugging up open knock-outs is the way to avoid all the rebuild issues.

 

[Freddmc]

If you haven't already done so go to Smokstak.They have a separate forum for Onans. I have a older Onan and go there for advice and parts.
Also go to this guys site.(http://www.beginningfromthismorning.com/) He is converting a bus for full time living.He has dozens of very informative videos outlining all the various tasks in converting the bus. Of particular interest to you will be the electrical components including how to convert a Leaf lithium battery pak, expanding solar panels etc. Of particular interest is the fact that he can run 3 A/C units FROM THE SOLAR PANELS alone. And you can email him with specific questions. He has a lot of videos on his site and it can be a little difficult to navigate but its all there. For every video there is also a written explaination of the task performed.