Onan Genset Shuts Off When On Road With Outside Temperature 90 Degrees Plus

[LR]

I have 2004 Onan Marquis Gold 5500 GenSet that works fine in place below 90 degrees outside temperature. It has worked just fine for the first 12 years yin all condintions,but now, when I get on the road in temperature over 90 degrees, it shuts down. it is in my 2004 Winnebago Adventurer 38J motorhome. I have spoken with the Onan tech and they suggest installing a baffle to keep the GenSet cooler or install a new fuel pump. Has anyone had a similar problem?

[kevin1959]

I have a 2013 Adventurer and towards the end of last year, mine shut down a couple times while driving. Reading your post reminded me of it. I'll be watching this thread closely now.

[lotsoftoys]

If the generator is mounted on the passenger side, the cooling air inlet is behind the outlet and recirculation of the hot cooling air can be an issue. Even is the generator is mounted on the driver's side in the back, I have heard of a few shutting down on rough roads. Do you notice it shutting down more when you hit a bump or on rough roads?

Fuel content with the addition of ethanol has also changed and seems to vaporize at a lower temperature. Also the generator is likely a little dirty and doesn't cool as good as it did new. Suggest you remove the generator door and blow off the cooling fins with compressed air. Do NOT use water.

[Gormleys]

Our old MH (Thor ACE) had this problem. It was definitely related to heat. In it, the gas vaporized in the fuel line going to the generator. Adding an inline fuel pump fixed it, though others also added new vents and heat baffles.

[azpete]

when traveling in higher temps, i change oil to 50 wt. either 20w 50 or similar. that has worked for 40 years for me. also keep oil level to full. when you brake, the oil sloshes to one end of the sump, and the low oil switch shuts the gen down
others may hav e a different opinion, but as a service manager and tech for more than 40 years. i do what works for me.

[LR]

Update. My Onan 5500 Generator was shutting down when the outside temperature was above 90 degrees. Solved the problem by replacing the fuel pump.

[redcolorado]

Thanks for the update. I have the same generator and will keep this in mind should I have the problem.

[Atom Ant]

Good deal! Glad its fixed.

On the baffle, we had to install one on a 6500 because it would overheat stationary, but never rolling. Its air cooled with a fan that pulls air from below and discharges it back down to below. On hot pavement in would just cycle the heated discharge back through until progressively it climbed in temp and overheated. The baffle minimized that somewhat.

[Raylance]

I had the same heat related problem. A new fuel pump fixed it.

[Rsimonton]

Would you describe the baffle, is it deflecting the hot air away from the intake of the genny? Is this an Onan part or custom fabricated. Thanks

[Atom Ant]

I honestly don't know on mine if the Dealer made it or Onan provided it. It was Onan's recommendation to the Dealer to cure our symptom, and it seemed to work.

The problem was when 5ers went to that Z-frame to increase the basement size, which put the generator much closer to the ground than they had been before. On a hot day the baffle just diverted the heat away so it didn't just bounce off the hot pavement and come back in. It was a curved piece of metal, so it may have been an Onan part.

[jpmihalk]

Same as others have said, on our 98 Itasca we had to replace the fuel pump to allow the unit to run in hot weather.