Replacement for Onan 4000

Won't cut it, Cody. Your AC + converter will require approx 2000-2200 watts, steady state. Note that this genny will deliver 1600 watts steady state; not 2000.

Suggest you not give up on the Onan just yet and, instead, find someone who will troubleshoot it rather than throw parts at it. The fuel pump/filter often are culprits; I actually had to replace the magneto in mine (rare problem) and it has been running fine for 4 years since.

Others will have advice as well......there are a LOT of satisfied owners out there and many have a ton of expertise as well.

Good luck on the fix.

Exercise makes all the difference, but a periodic tune up still costs money. We don't use ours much but ac is necessary every so often. I can refer you to KD Repair, a good shop if you're social distancing around Chicago. :-)

I would give up on the Onan as they are nothing but trouble and parts are expensive. I haven’t met an Onan that I liked yet! Buy two Honda 2000 watt generators and link them together to get 4000 watts. I did this years ago and couldn’t be happier. I do have to start by pulling but they always work. If on a tight budget then get the Champion version. You’ll only over spend and get frustrated with your Onan. Good luck!

Onan generators reliable/workhorses that tend to outlive the RV - but they do need to be exercised monthly to insure that the carburetors don't gum up. Use the forum search feature using the term Seafoam and Generator ... lots of threads on how to restore carb function using Seafoam.

Your problem is that you have a 5 year old generator that only has 80 hours on it. That's not even one full day a year. Gensets need to be run - a lot and under load. At this point it should have a few hundred hours. It's better to run a generator 24/7 than let them sit not running at all. Hard to tell what's wrong with it since it doesn't get used. But your Onan was built for your RV. It's sized properly and fits in the bin, all the wiring is set up as well as fuel lines etc. I would get it fixed rather than buy another generator. Otherwise you have a lot more work to do, like where to put the new one, wiring it up, fuel supply, ventilation and exhaust, etc etc. The root problem is lack of use and maintenance. I don't see how buying another generator will fix that problem. Do you even need a generator? Seems like you don't use the one you have. Not trying to be snarky. But fixing this one will likely be cheaper and easier than buying another one and getting that to work in your rv.


On edit:
I reviewed a few of your other posts an it seems like you have an RV that only gets used 1 or 2 times a year. As a result you are having issues due to lack of use. RV's - like anything else - like to be used or they start to have problems. Have you considered that you may actually be spending more money addressing things from lack of use than selling it and renting an RV for the 1 or 2 times a year? Again, not trying to be snarky, just a thought.

:), at least run the genny.

If you choose the portable genny route, then you have to be concerned about someone walking away with it. You have be able to always hide it when not using it. Someone told me about one being chained to a tree while the owner was away off his site. When he returned, the tree and the genny were gone. Just sawdust remained.

In order to run an AC unit of 13,500 or larger , you will need two paired 2000's because a single larger unit like a 100 plus lb. 3000 will probably be heavy to lift and move around.

If you choose to go the portable genny route, they too need to be exercised the same way as any other generator.
If you choose two Honda 2000 or similar, you will need optional pairing cord and rv converter plug for the 30 amp outlet. Each genny will weigh about 50#, make sure you can handle lifting that weight in awkward positions. You know, as we become younger all that stuff becomes easier. :)



I think you should drive the rv to go shopping or whatever, run it , you are doing more harm parking it and leaving it.


I would do a full service on the Onan. Whatever needs to be done but at least a fuel filter and oil change once a year.

When you turn off an Onan, shut off any load on it, then shut it off. This reduces premature failure of certain parts, like the voltage regulator.

When you store the rv, try to find non ethanol gasoline. Google search near you then call to confirm they have it.
it will be a higher octane fuel but well worth it.
Stabilize your fuel, Sea Foam, StarTron or the blue Marine Stabil all work well, read the amounts needed on each bottle.

Once you add stabilizer your fuel, drive the rv while running the generator to transfer the stabilized fuel throughout both rv and generator lines. Now, when you start the generator once a month for 30 mins, the generator fuel lines will remain protected.

In my industry we had maybe 500 Onan generators and they proved to be a workhorse and very reliable. They need to be run and run a lot.
Replacing with portables seems to be a costly solution to a small problem. Storing them, carrying fuel....no thanks.....

Servicing your unit then using it like it was designed to do may be the best option for both ease of use and dollars spent.

Portable units. Always turn the fuel supply off and let the unit run out of fuel. This will prevent fuel from gumming up in the carburetor.

I have a 10 year old Champion that has seen plenty of abuse. It sits sometimes for months and once i turn on the fuel, wait a minute, half choke and half

a pull it starts right up. i started using non-ethanol gas in my saw and rototiller. I still include fuel treatment though.

Let me start with I am biased and would not take an Onan for free. Paying for parts is one thing, I refuse to own something where I get ripped off for parts. I had a nice Honda EV4000 and let it go with an RV I sold and have kicked myself ever since.

So I have my nice little Toyota set up with a 8000 btu window AC and run it with a Honda 2000. The Honda is in a sound box, basically an modified aluminum truck tool box. Could it be stolen, of course they could also take the whole RV!

There is one option for running An AC with small generators, I have not tried it yet so will not recommend. If needed I would spend my money on one!

https://www.microair.net/collections/easystart-soft-starters/products/easystart-364-3-ton-single-phase-soft-starter-for-air-conditioners?gclid=EAIaIQobChMI14Ko2q3K6AIVB2KGCh2kYwBoEAQYAiABEgJzTPD_BwE&variant=30176048267

They tell me Honda replacement parts are expensive, I do not know as in 20 years I have never bought a replacement part. Except for a pull cord and that was generic!

Had my Onan rebuilt after 1400 hours on it since I boondock a lot. Cost about $1800 for everything and now have 1700 hours. I turn it on to run microwave while cooking and couldn't imagine having to go outside in weather to pull start the generator(s) each time. As with all mechanical things, you gotta use'em or lose'em.....sitting idle just doesn't work well.

Wonder why Honda stopped making generators??.....if it was an upgrade to an Onan, why is it no longer available? I love my honda truck and grass mowers and just a sincere question.....why don't they do RV generators?

VA-Apraisr wrote:
Had my Onan rebuilt after 1400 hours on it since I boondock a lot. Cost about $1800 for everything and now have 1700 hours. I turn it on to run microwave while cooking and couldn't imagine having to go outside in weather to pull start the generator(s) each time. As with all mechanical things, you gotta use'em or lose'em.....sitting idle just doesn't work well.

Wonder why Honda stopped making generators??.....if it was an upgrade to an Onan, why is it no longer available? I love my honda truck and grass mowers and just a sincere question.....why don't they do RV generators?

X2 here on what you say about your Onan!

We've had an Onan 4000 in our Class C for around 14 years now, and it's never let us down. I try to run it 1/2 to 1 hour every month with a load on it.

I also carry a little super quiet 650 watt Honda portable along with us for just-in-case backup. The little EX650 Honda is at least 30 years old and still starts up on the 1st or 2nd or 3rd pull. I've only had to replace a small section of it's rubber gas line. Some years ago I installed an E3 spark plug in it for added reliability, plus I use synthetic Mobil 1 oil in it. I also use an E3 spark plug and Mobil 1 oil in the Onan:

https://e3sparkplugs.com/