Help! My Generator runs but I don’t have any power!

 Help!  My Generator runs but I don’t have any power!

Last fall we wrote about how to check the oil in your Onan 2500/2800. The next thing to know is how to reset the circuit breaker on the Onan.

If you try to run too many high power devices,  such as a microwave and hair drier,  at the same time you are likely to trip the circuit breaker on the Onan.  By high power we include things like the air conditioner and perhaps your coffee maker.  Don't run more than one of these at a time.  Your generator is also recharging your house battery or batteries,  so you may be drawing more power than you know about.  You might hear the generator struggle and then die.  The generator may restart just fine, but even after the short built-in delay you may find you have no power in your camper.  You probably just tripped the Onan circuit breaker.  It is easy to reset, but is not be easy to get to it.

Underneath Onan
Roadtrek with Onan mounted underneath

Sometime in 1996, Roadtrek moved the Onan from a side compartment to under the vehicle in the center rear.  So crawling underneath is necessary.  If you are physically not able to crawl under your camper, you may still want to know what to do and have photos.  Then you can ask the young guy in the next campsite to do it for you.  This photo is a 2800 (gasoline model) under a Roadtrek.

Compartment Onan)
Roadtrek compartment mounted Onan

If you have a side compartment-mounted Onan,  you won't have to do any crawling.  Either way, pull the two latches at the bottom of the access panel cover up and then out to remove the black panel.  Be careful to reinstall the access cover securely.  It is necessary for proper air flow when the generator is running and it is very expensive to replace if you loose it.

Onan Labeled Parts
Onan Labeled Parts

Behind the access panel you will find this if you have a 2800.  The 2500 is the propane model and it will not have a carburetor.  If you are lying on your back under your Roadtrek you may have to identify parts by feel.  Click on photo to view in larger scale.


Onan Circuit Breaker
Onan 120 volt Circuit Breaker

The circuit breaker is located on the side of the control panel below the 5 amp 12 volt fuse and next to the fuel filter.  To reset the circuit break flip the switch up and down a couple of times, but be sure to leave it in the up position.  You will probably have to do this all by feel.


Onan Circuit Breaker 2
Close up of Onan Circuit Breaker

This photo clearly shows that the up position is “on”.  This photo was taken with the Onan disassembled, so you cannot actually see this perspective in an operating Onan.

We hope resetting the circuit breaker will restore power inside your camper.  If not, check first the main circuit breaker at your electrical panel.  If that is not the problem you will need to trace the power lines from the Onan to the electrical panel to find the problem.

If you want to understand more about your Roadtrek's electrical system, check out John Slaughter's Roadtrek Electrical Simulator.

Now you have learned one more thing that every Onan 2800/2500 owner needs to know!



Roger and Lynn Brucker

Roger Brucker and his wife Lynn have been Roadtrekkers since 2009. Both are retired, Roger from a Business-to-Business advertising agency and from teaching marketing for 25 years at Wright State University, Dayton, OH. Lynn is an electronics engineer, retired from the USAF Research Laboratory. Roger has authored or co-authored five books on cave exploring. They are cave explorers, kite flyers, and have four Standard Poodles. Their home base is Beavercreek, OH, a Dayton suburb. “We’ve done a lot of camping and long distance tandem bicycle riding, including an unsupported San Diego to St. Augustine ride in 2000,” said Lynn. Roger says, “But we love our 190 Popular Roadtrek because we can go anywhere on a moment’s notice, and stay off the grid for a week.” They are known to many Roadtrekkers for contributing ideas and suggestions on the Roadtrek Yahoo Forum and Cyberrally. Some of their modifications to Red Rover, their Roadtrek, are documented at


  • Check the breaker(s)

  • Transfer switch or power cord (if no transfer switch)

  • I agree with Les that you should check that the power cord is plugged into the coach. If not, it is most likely a fuse or breaker that has blown or is tripped.

  • We just had our transfer switch replaced on our eight year old 210. Not a cheap repair.

  • If your engine runs, but the generator is not producing electricity, it may need to be “flashed”.

    Google “flashing the field” for detailed instructions…

  • Thanks Mike Wendland this is the source we used to restart ours yesterday!

  • Thank you Mike, no problems yet with hour’s.

  • Durn auto-correct.

  • All the class Bs I know with a built in generator are using the Onan 2500/2800 wired through a transfer switch. If the generator was producing power and suddenly is not, the breaker in the Onan is the most likely cause. It could be the coach circuit breaker (which is lots easier to reach) but that is rarely the case. Yes, it could be something in between the two breakers (like the transfer switch) but that is rare. If you look at the Onan Service Manual it will tell you the causes of “generator runs but no power”. Here is our Onan Troubleshooting guide. See the bottom of page 2 for this problem.

  • We have a class A 2002 Monaco Windsor with 7500 Onan generator. It’s our first RV and we’re just learning about this whole new experience. Recently during last trip our generator experienced problem described in article above. It was really hot outside and both of our ac units were on (dash ac doesn’t work so we had to run both ac’s in the coach plus fridge, coffe maker, phone charger, etc…). All of the sudden generator started struggling a bit, turning itself off a few times until the power would no longer work while generator was on. We researched for this problem and came across this page. Turns out it was the circuit breaker switch! Quick, easy and free fix! Thanks guys for your help! We now plan to service our gen so it keeps working well in the future.

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