Your RV generator is easy to ignore — right up until the 108° afternoon it decides to quit. Preventive maintenance is the single cheapest way to extend the life of an Onan, Cummins, or Generac unit and avoid the emergency call. Here's the maintenance schedule we recommend after years of servicing these units in Phoenix heat.
Every 20 hours (or after long trips)
Visual inspection. Look for oil leaks, loose belt, obvious fuel smell, or debris around the intake and exhaust. Wipe down the housing. Verify the air intake isn't blocked. Two minutes of attention now saves you hours later.
Every 100 hours or 6 months
Change oil and oil filter. Most RV generators run harder than a car engine per hour — high load, hot ambient temps, and short cycle times. Fresh oil matters. Use the manufacturer-spec weight (usually 15W-40 for diesel Onans, 10W-30 for most gas units). Check and clean the spark arrestor on the exhaust.
Every 150 hours or annually
Full tune-up. Air filter, fuel filter, spark plug replacement on gas units, injector inspection on diesel. This is when we also recommend a load-bank test — running the generator at rated load for 30 minutes to verify voltage regulation and confirm the windings can carry demand. A generator that starts fine but can't hold load is a common failure mode, and load testing catches it early.
Every 400 hours or 2 years
Coolant service on liquid-cooled diesel units (larger Onan Quiet Diesels, Kohler, Cummins). Check the belt for cracks and glazing. Inspect the fuel system for varnish or algae, particularly on diesel units that don't get run often.
Exercise it monthly — under load
The most important habit: run your generator monthly, for 30 minutes, under load. That means turning on the air conditioner, microwave, or an electric heater — not just idling with no load. Idle running actually damages generators over time by fouling plugs and glazing cylinders. Under-load exercise keeps everything lubricated, keeps fuel fresh in the system, and catches problems while you're at home, not stranded.
Storage prep
If you're not going to use the RV for three-plus months, do a proper storage prep: stabilize the fuel, run the generator until stabilizer is through the whole fuel system, then top off the tank to prevent condensation. Better yet: don't store it that long. Run it monthly.
Book a generator tune-up or full service anytime: (602) 696-8672.