Saturday, September 23, 2023


Onan generator conks when parked – RV Consumer Support

By Russ and Tiña De Maris
Pat K. responded to our offer to help RV consumers with problems. In his 2018 Coachmen Freelander, Pat has a 4,000-watt Onan generator. Having a genset is a great help when camping, and Pat really enjoys his. Trouble is, Pat’s Onan generator conks out when he parks the rig. Here’s his description:

Mis-calibrated dipstick on the Onan generator?

“We travel with the generator on for a couple of hours. When we get to the campsite to fill with water, the generator stops.” It’s not just a fluke, this misbehavior repeats itself, and is driving Pat crazy. He told us he’d seen a video on the internet where he learned that some folks say the dipstick on some Onan generators is not properly calibrated As a result, suggests the video, these generators are getting overfilled, and not running properly. Pat checked it out by suctioning out some of his oil, but the Onan generator still conked. He wonders if he still might be facing an overfill, or perhaps an overheating condition.

Our resident RV technician, Dave Solberg, cocked his ear to Pat’s predicament and responded with a few thoughts to check out. We’ve shared them with Pat, and we’re passing them along to you, just in case you’ve got an unruly Onan.

The Tech Man speaks

First, Dave agrees with Pat. The symptoms exhibited by this grouchy genny would well point to either an oil overfill, or an overheat condition. Since Pat already tried reducing the amount oil in the cranky one’s crankcase, Dave suggests a couple of other lines to follow.

First, Dave says, “Change the oil.” He points out that Onan generators have a reputation of being pretty finicky about what goes “under their hoods.” To that end, our tech guru advises sticking to Onan specified parts. However, he does suggest that changing out the oil with synthetic may help if the situation is due to overheating. But when it comes to filters of any sort, Dave comments, “I would change the oil and air filter again, ONLY with Onan-recommended parts. Aftermarket filters can really cause issues.”

Onan generator hates Hades

Other issues that can raise Cain and possibly cause an Onan generator to conk are also related to heat. Ethanol gasoline burns hotter than non-ethanol. Trouble is, when your generator sucks its gas from your motorhome gas tank, you probably don’t have much choice about what’s in the tank. But the higher the ethanol content, it would seem the greater the issue. But there’s still more to think about when it comes to heat.

Dave Solberg’s suggestion to Pat is this: Once the oil and filter swap outs are completed, try another test run. Does the generator work fine while cruising down the road, but still conk out when parked? If it does, crank open the generator bay door and park a big cooling fan outside. Blast the running, but parked, generator, with outside air. If the generator responds to this cool trick and keeps running, then you’ll know you have a heat issue to deal with.

Pat hasn’t had the time to put Dave’s suggestions to work. We’re hopeful that the recommendations will de-aggravate the stubborn generator, and Pat will have generator availability on the run, and in the shade.

Have you got a problem?

Have you got an issue you can’t figure out? Had problems with an RV manufacturer, dealer, or a related business? Drop us a line using the form below, and we’ll see if we can help!

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For more stories from Russ and Tiña De Maris

More tech help from Dave Solberg


Russ and Tiña De Maris
Russ and Tiña De Maris
Russ and Tiña went from childhood tent camping to RVing in the 1980s when the ground got too hard. They've been tutored in the ways of RVing (and RV repair) by a series of rigs, from truck campers, to a fifth-wheel, and several travel trailers. In addition to writing scores of articles on RVing topics, they've also taught college classes for folks new to RVing. They authored the book, RV Boondocking Basics.


  1. Had a similar problem where after generator was running for a few hour it would shutdown and not restart until it cooled down. Long story but found fuel pump would quit when hot. Replaced and all was good.

  2. Put the green thing in the river. Get a red one. Smaller, cheaper, more reliable, and much quieter. Or get a blue one for the same reasons.


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