By Greg Illes
Onan generators, typically 4000W (3600W for propane), are often a feature on mid- to large-size RVs. You can recognize these ubiquitous products by the presence of a large green box in place of a storage compartment.
While generally quite reliable, these units have a failure mode that is deceptively complex, yielding an error code that essentially says, “Take me to your Onan service shop.” If you own or operate an Onan, there’s an easy maintenance action you can take to prevent failures and expensive shop visits.
Inside the generator cover (two hand levers to open) you will see the engine and its carburetor at the upper right. On top of the carburetor is control linkage that governs the speed of the engine under different load conditions. If this linkage gets dirty, dusty or corroded, it can start to bind up. Since it’s operated basically by air pressure from the cooling fan, it doesn’t take much to get it “sticky.”
This happened on my RV after several miles of dusty roads. I heard the generator “rev up” a little bit one day after the microwave shut off, and then the generator shut down and delivered an error code 14 — “Overfrequency Fault.” Normally, such a fault is due to electronic failure in the generator electronics. But in this case (and several times since), the issue was simply that the feedback linkage could not respond quickly due to dirt accumulation, and the motor over-revved.
Blowing out the accumulated dust and putting a small drop of Tri-Flo on the pivot points was all that it took to get my volts and watts flowing smoothly again. Now, I do this proactively whenever I’ve been in dusty conditions, or if it’s just been a long time since I cleaned up.
A compressed air source helps a lot, but if you’re out on the road and don’t have such access you can get the linkage free just by wiggling it full-stop by hand (of course, don’t do any of this with the generator running). If you see evidence of crusty corrosion, use a TINY bit of lubrication — just a drop of WD-40 or light oil will do. Too much lube will only hasten the accumulation of more dirt.