Onan RV generators: what fails in Bakersfield and what repairs cost

Onan is what is mounted in most motorhomes and a good many fifth wheels, and in Kern County it fails in one dominant way: it sits, with fuel in it, through a hot summer. Almost every generator call we take traces back to stale fuel, valley dust, or both.

The fuel problem, in detail

Modern pump gasoline is not a storage fluid, and heat accelerates its breakdown. Ethanol-blended fuel left in a carburetor bowl through months of Bakersfield summer, where sustained heat above 100 degrees is normal for weeks at a stretch, separates and leaves a varnish that sets in the carburetor’s small passages, measured in thousandths of an inch.

The result is a generator that cranks fine and will not fire, or fires and dies, or runs and surges. All three are the same underlying fault and all three are fixed the same way: the carburetor comes off, gets cleaned or replaced, and the fuel system gets checked back to the tank.

What things cost

Same approach as everything on our pricing page: diagnose, quote, get your approval, then work.

The failure order on these units

1. Fuel system, by a wide margin, for the reasons above.
2. Air filters and intake, loaded faster here than in a lot of climates by agricultural and oilfield dust. A partially clogged filter starves the engine and causes rough running and hard starting well before it looks visibly ruined.
3. Corrosion on connectors and grounds. Less of a factor in this dry climate than in a humid one, but dust intrusion into connectors on an exposed harness still causes intermittent faults.
4. Oil, which on a generator is measured in running hours and is routinely never changed at all. Generator hour meters exist for a reason.
5. No AC output with the engine running happily. This is the electrical side: brushes, capacitor, voltage regulator, or a tripped breaker on the unit itself. The good news is that it means the engine is fine.
6. Starting and control faults, including the remote start panel and its wiring.
7. Exhaust, a safety item rather than a performance one, covered below.

The habit that prevents nearly all of it

Run it for two hours a month under load. Not at idle, not for five minutes. Under load, meaning with an air conditioner running, long enough to get everything hot.

Owners who do this essentially never call us about a generator that will not start. It keeps fresh fuel moving through the bowl, burns off deposits before they set, circulates oil, and exercises the start circuit. It is free, it takes no skill, and it is the most effective maintenance advice on this entire site.

If the rig genuinely has to sit for months, the next best options are treating the fuel with an ethanol-rated stabilizer and running it through, or shutting off the fuel and running the bowl dry where the unit allows it.

Heat, dust, and honest expectations

Generators are rated under standard conditions, and output falls somewhat as intake air temperature rises, because hot air is less dense. On a 108-degree Bakersfield afternoon your unit may not quite make its nameplate number, and if it has always struggled to carry two rooftop air conditioners at once, that can be physics as much as a fault. We will say so instead of selling you a rebuild.

The practical fixes for that are cheap: stagger the AC starts rather than letting both compressors hit at once, and consider soft-start devices on the air conditioners, which dramatically cut inrush current. Many “my generator cannot handle my rig” complaints are solved for a fraction of any repair.

The safety paragraph

Two things we will always raise:

Exhaust integrity. A leaking generator exhaust on a motorhome is a carbon monoxide risk. These systems can develop leaks at joints and mounts over years of vibration and heat cycling. If we find one, we will tell you and we will recommend not running the unit until it is repaired.

Your CO alarm. Check that it works and check its expiry date, because they do expire. That is free advice and it is the most important sentence on this page.

The generator repair service page covers the full scope of what we do on site, across Bakersfield, Oildale, Rosedale, Shafter, Taft, Tehachapi, and the Kern River Valley, where a working generator often matters most, at a campsite with no shore power at all.