Thursday, September 21, 2023


Why does my RV’s generator stop running while driving?

Dear Dave,
I have a 2022 Thor A.C.E. Class A motorhome and the generator shuts off while traveling. I checked all items: oil, cables, batteries, and voltage. —Eugene, 2022 Thor A.C.E. 33.1

Dear Eugene,
There are several things that could cause the generator to stop running while driving. First, it could be getting hot. Most people don’t believe that because traveling down the road should provide superior airflow versus sitting. However, since your vehicle is a Ford F-53 gas chassis, the engine is up front, and the exhaust runs back towards the generator compartment. All the heat from the engine and exhaust as well as the road can swell up in the generator compartment and cause excess heat. I have found installing a diverter or heat shield helped in this situation. I’ve even cut a vent hole in the back.

Next, I would change the oil and filter and use Onan oil and filter as recommended. Make sure it is spot-on for level! Using an aftermarket oil can be either too heavy or too thin, even though the viscosity shows the same. This also goes for the air filter, as it needs proper airflow.

What type of fuel are you using?

Fuel is the next area I would look at. First, what type of fuel are you using at the pump? Your generator is pulling the same fuel as the engine from the fuel tank. A cheap fuel or higher ethanol mix will burn hotter. I try to use non-ethanol fuel in all my small engine components. You might want to look at what is going into the tank. It might be getting too hot going down the road with the combination of that and the engine heat.

Also, the fuel pump and fuel filter might be weak and create an insufficient flow or even vapor locking situation. Finally, one of the most simple of fixes could be the fuel cap is not venting properly, which would also create a vapor lock situation. Try loosening it slightly to see if that helps.

 You might also enjoy this from Dave 

No power is coming from my RV’s onboard generator. Why?

Dear Dave, 
The Onan generator starts and runs perfectly, but when I start it, it’s not powering up the RV. —William, 2017 Fleetwood Flair LXE

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


  1. For me, it was Dave’s last suggestion that cured this problem. I changed both the fuel filter and pump and the problem is solved! Not only that but it starts faster too.

  2. If the Onan brand oil viscosity is different than other brands even though the viscosity shows the same, I’m not sure I want an Onan generator. What are you supposed to do in a pinch if you need oil and no Onan brand oil or filter are available?

    • As long as the oil that you are using, meets the SAE requirements that Onan specifies, there should NOT be any problem. Most manufacturers of internal combustion engines will recommend their own name branded products. Requiring them is unlawful unless they provide them at no cost to the consumer.

    • If what you are referring to is “no ethanol” or “ethanol free” then absolutely it is the best fuel for a gas generator. But since an Onan in a class A or C probably shares fuel with the engine it would be an extra pricey fill!

      • Thanks Bill. Yes, that WAS what I was referring to. I’m going to switch all my generator gas jugs to ethanol just as soon as I put THAT gas in my wife’s car . . . I have three generators sitting in different outbuildings.

  3. As the first poster wrote about gas tank
    Missed the obvious
    More than once has my generator quit because it ran out of fuel
    I added a 10 gallon stainless steel custom gas tank just for the Onan
    That way I can put fuel preserves in the generator

  4. Another possibility is it’s starving for air. While driving, the RV is creating high and low air currents around the sides which may act like a vacuum. Similar to the suction produced by a semi truck. Next time it happens, you may be passing or being passed by a large truck.

  5. Maybe the generator is running out of gas. Our generator shares the gas tank with the motor home engine. The fuel pickup for the generator is higher in the tank than the pickup for the engine. That’s so the generator won’t run the tank empty. Our generator quit one day, in our driveway, while I wasn’t paying attention. Oops! Filled the tank and the generator worked again.

    • As Dan says .. Most Onans in a class A or C that don’t use propane share the vehicle fuel tank. They are usually designed to stop drawing fuel around the 1/4 full area on the dash guage. 1st thing that should have been recommended to determine in my opinion.


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