An RV generator is a small engine that spends most of its life doing nothing — and that's exactly the problem. Engines hate sitting. Fuel goes stale, carburetors gum up, seals dry, and batteries self-discharge. The owner who "didn't do anything to it" is precisely the owner whose Onan won't start on the one weekend it matters. Trip-ready power is a habit, not a repair.
Rule #1: Exercise the generator — under load
This is the single most important thing you can do, and most owners skip it. A generator that sits for months develops fuel and carburetor problems that a little regular running prevents entirely.
- Run it about 2 hours every month, even in storage.
- Under load — turn on the A/C, microwave, or an electric heater. Running it with nothing plugged in ("no load") actually causes carbon buildup; it needs to work.
- Let it reach operating temperature — a quick 5-minute run does more harm than good.
✅ Put it on the calendar
Set a monthly reminder to run the generator under load for two hours. This one habit prevents the majority of "won't start" service calls — and it's free.
Fuel: the silent killer of stored generators
Modern ethanol-blend gasoline starts degrading in as little as 30 days and attracts moisture. Diesel fares better but grows algae and gels in cold. Either way:
- Add fuel stabilizer before any storage over a month (gas rigs especially).
- Keep the tank fuller in storage to reduce condensation — most RV generators pull from the main tank, so a topped tank protects the genset too.
- Note the ¼-tank cutoff: most motorhome generators stop drawing fuel when the main tank hits about a quarter — a safety reserve so you can still drive. Plan boondocking fuel accordingly.
The service items owners forget
| Item | Interval (typical) | Why it matters |
|---|---|---|
| Oil & oil filter | ~150 hrs / annually | Small sump, works hard — dirty oil kills it fast |
| Air filter | Inspect each service | A clogged filter fouls the mixture and soots plugs |
| Spark plug (gas) | ~250–400 hrs | Hard-start and rough-run culprit |
| Fuel filter | Per manufacturer | Stale-fuel debris starves the carb/injectors |
| Spark arrestor / exhaust | Annually | Carbon buildup + a real fire-safety item |
Check your Onan or Cummins manual for exact hours — the hour meter, not the calendar, drives most of these. But calendar matters too: a generator that runs 20 hours a year still needs annual oil because oil degrades sitting.
Don't forget the batteries
Half of "electrical" problems on an RV are just tired batteries. There are usually three systems, and each strands you differently:
- House bank — runs your lights, water pump, and 12V gear. Lead-acid banks left discharged sulfate and die young; keep them charged in storage or pull them.
- Chassis battery — starts the motorhome. A dead one on travel day is a tow, not a trip.
- Generator start battery — on many rigs the genset has its own; some pull from the chassis battery. Know which you have.
⚠️ Storage is where batteries die
A "parasitic draw" (propane detector, stereo memory, control boards) will flatten a disconnected-feeling rig over a few weeks. Use the battery disconnect, or better, a smart maintainer, whenever the rig sits.
Shore power, converter, and inverter
Round out the picture: your converter charges the house bank and runs 12V gear on shore power; your inverter (if equipped) turns battery power into 120V for outlets off-grid. Protect all of it with a quality surge protector / EMS at the pedestal — a bad campground post can fry a converter, and that failure hides as "my batteries won't charge."
🛡️ Trip-ready beats roadside
A pre-trip generator run and a battery check take 20 minutes. A generator that won't start at a full campground on a 95° night can't be fixed with 20 minutes — or often, that weekend at all.