The "Exercise" Routine: Why RV Generators Fail from Disuse
If you own a motorhome, you know that your generator is the ultimate unsung hero of the open road. It’s the magic box that lets you pull into a quiet clearing deep in a national forest without sacrificing the "home" part of your motorhome. It keeps the beer cold, the AC humming, and the microwave ready for a midnight snack.
Why is Avoiding Generator Use Actually Costing You Money?
There’s a common, and expensive, misconception out there: the idea that by "saving" your generator and rarely turning it on, you’re somehow extending its life.
In the RV world, the opposite is actually true. A generator that sits idle is a generator that’s slowly dying. At Mainline RV & Truck Service, we see units come in for RV generator repair all the time, not because they were overworked, but because they were ignored. They simply "lost their muscle" from a lack of exercise.
In this guide, we’re going to break down why "rest" is actually your generator's worst enemy and share a simple routine to keep your power plant healthy, happy, and ready for your next adventure.
The "Varnish" Problem: How Old Fuel Kills Carburetors
The number one reason a generator might crank but refuse to start is that the fuel is going bad. Today's gasoline contains ethanol, which breaks down very quickly, often in just 30 days. When fuel sits in the generator's small carburetor bowls and tiny passages, its chemical composition begins to change.
As the lighter parts of the fuel evaporate, they leave behind a thick, sticky residue. Experts call this substance varnish. The gummy residue clogs the microscopic jets that manage the fuel flow. Once these jets are blocked, the engine either cannot start at all or will run very lean, which causes overheating or stalling.
Because many RV generators (especially popular Onan models) rely on finely tuned carburetors, even a tiny speck of varnish can ruin performance. In many situations, these carburetors cannot be easily cleaned and require a complete replacement. Running the generator regularly avoids this issue entirely by circulating fresh fuel and stopping the stagnant chemical reaction from ever starting.
Beyond Fuel: The Danger of Oil Oxidation and Moisture
While problems with fuel often get the most attention, the generator's internal lubrication system also suffers greatly when stored for long periods.
When an engine is off, the oil naturally drains away from the upper parts of the cylinders and other internal components, leaving them exposed to the air. Over time, humidity in the air can lead to condensation and moisture buildup inside the crankcase. The moisture then mixes with the oil, creating an acidic sludge and speeding up oil oxidation. Oxidation reduces the oil's ability to protect the engine when you finally do turn it on.
Moreover, the electrical side of the generator, the stator and rotor, can develop surface corrosion or "glazing" if they are not used. Running the generator creates heat, and that heat is what naturally dries out any accumulated moisture in the electrical windings, which prevents short circuits and keeps your power supply reliable.
The Step-by-Step Guide to "Exercising" Your Onan Generator
To avoid a very expensive trip for Onan generator repair, you absolutely need to start a monthly exercise routine. Just letting the generator idle is not enough; you must run it with an electrical load. Here is the professional advice for keeping your unit operating at its best:
- Check the Fluids: Before you start it, check both the oil and coolant levels. Make sure there are no rodent nests, as they sometimes move in during storage.
- Start and Warm Up: Start the generator and let it run for approximately two to five minutes with no appliances turned on. That allows the oil to circulate throughout the engine and the engine temperature to settle.
- Apply the Load: Everyone agrees this is the most important step. Turn on something that requires a lot of electricity. For most motorhomes, this means turning on the Roof Air Conditioner (during summer) or an Electric Space Heater (during winter). Your goal is to get the generator to about 50% of its total rated capacity.
- Run for Two Hours: Let the generator run with the load for a full two hours every month. Doing this ensures the engine gets hot enough to evaporate moisture from the oil and effectively scrub the internal electrical components clean.
- Cool Down: Turn off the air conditioner or heater and let the generator run without any load for another five minutes to cool down before you turn the entire unit off.
Signs You Need Professional Onan Generator Repair
Even with your best efforts, time can sometimes cause issues. If you follow the exercise routine but notice the following problems, it is definitely time to call a professional motorhome repair service:
- Surging or "Hunting": If the engine speed constantly goes up and down (it sounds like vroom-vroom-vroom), the generator is struggling to maintain a steady speed. That usually means there is a partially blocked carburetor or a failing governor component.
- Smoking: If you see blue smoke, it means oil is burning. Heavy black smoke points to a problem with the fuel-to-air mixture.
- Shutdown Under Load: If the generator runs fine until you switch on the A/C, and then it immediately dies, you have an issue with either the voltage regulator or the fuel delivery system's ability to manage a high demand.
- Leaking Fluids: You should address any signs of oil or coolant pooling underneath the generator tray right away to avoid a serious engine breakdown.
Prevention is Cheaper than Replacement
Buying a new RV generator can cost thousands of dollars, not including the labor for installation. By contrast, one bottle of fuel stabilizer and two hours of exercise once a month costs almost nothing at all.
If your generator has been off for six months or longer, you should not be surprised if it struggles to start. In these situations, a professional tune-up, which includes flushing the fuel system, replacing the spark plug, and changing the oil, can often rescue a unit that seems ready for the junkyard.
Contact Mainline RV & Truck Service for Onan Generator Repair & More!
Mainline RV & Truck Service protects your RV lifestyle investment. Our expert Navistar-certified technicians offer comprehensive motorhome repair, specialized RV generator repair (including stubborn Onan units), engine diagnostics, brake work, trailer suspension, and electrical troubleshooting. Get the high-quality care your vehicle needs before your next trip.
Contact us today to schedule your maintenance appointment. We’ll keep your rig ready for the road, so you can focus on the journey ahead.
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