The oil in an RV generator compartment degrades faster than the same oil in an open engine bay - Florida's enclosed, unventilated generator compartments routinely reach 180 to 220 degrees Fahrenheit during operation, which is above the threshold where conventional motor oil begins to lose its viscosity protection. Most manufacturers specify 100-hour or annual service intervals assuming normal operating temperatures; Florida summer heat effectively compresses that interval.
Most RV owners think of the generator tune-up as the oil change and nothing else. The oil change is important - but in Florida the full tune-up picture includes spark plugs that have fouled from rich running, an air filter that has loaded up with the fine dust and humidity that Florida road conditions put into compartment air, and most critically, a load test that confirms the genset can actually sustain the wattage your air conditioner demands. A generator that starts and idles is not a generator that has passed service.
Jesse Marcer founded Triton RV Repair in 2014 with a focus on Florida's specific operating environment. Hot compartment air, high ambient humidity, ethanol-blend fuel, and the pattern of seasonal use with long storage periods between are conditions that shorten service intervals and require techniques that differ from what works in a mild climate. Every tune-up call includes a documented load test at full AC draw before the service is signed off.
Why Florida Shortens Generator Service Intervals
The generator compartment in a Class A or Class C motorhome is a sealed or semi-sealed enclosure located beneath the living space or at the rear of the coach. During operation, that compartment absorbs heat from the engine, heat from the exhaust, and solar loading from the exterior surface of the coach. In Florida's summer months, ambient air temperatures already start at 90 degrees or higher before the engine adds its contribution. Compartment temperatures of 180 to 220 degrees Fahrenheit are measured routinely during site calls, and some poorly ventilated installations reach higher.
Oil viscosity degrades at elevated temperatures. Conventional 10W-30 that would give reliable protection through an entire season in the Midwest may thin to the point of marginal protection within 60 to 70 hours of Florida summer operation. The oxidation process that turns clean oil into sludge also accelerates exponentially with temperature - a well-documented relationship in industrial lubrication engineering. Cummins Onan's own service documentation acknowledges that severe-duty environments require shortened intervals, and a Florida summer generator compartment qualifies as severe duty.
Ethanol-blend gasoline adds a second complication that is specific to stored and infrequently used gensets. E10 fuel - which is the standard pump gasoline in Florida - absorbs moisture from ambient air and can phase-separate over 30 to 60 days of storage, leaving a water-alcohol layer at the bottom of the fuel tank and carburetors. The result is hard starting, rough running, and carburetor corrosion that is not covered under warranty because the damage is storage-related. A properly conducted annual tune-up includes inspection of the fuel system for these signs and a carburetor cleaning if the symptoms are present.
What a Complete Generator Tune-Up Includes
An RV generator tune-up is not a single item service - it is a sequence of related tasks that only make sense when done together. Changing oil without changing the filter captures the same contaminated particles in the new oil within minutes of startup. Changing the filter without testing the output under load leaves the most important question unanswered. The full tune-up sequence Triton follows for most gasoline gensets covers the following steps.
Oil drain and refill starts with a warm engine so contaminants are in suspension rather than settled. The oil is drained completely, the drain plug inspected for thread condition, and the correct viscosity oil is refilled to specification - typically 15W-40 for Florida ambient temperatures on most Onan QG series units. Oil capacity is verified against the specific model, not assumed, because capacity varies from under one quart on smaller units to over two quarts on diesel gensets.
The oil filter is replaced every service without exception. Oil filters on small air-cooled engines are not designed to last multiple oil change cycles and the bypass valve inside the filter can stick open on a saturated filter, sending unfiltered oil directly to the bearings. The filter is inspected as it comes off - metal particles in the filter media are a diagnostic indicator of internal wear that needs to be caught before it progresses.
Spark plugs on gasoline generators are a consumable that most owners overlook because the engine still starts with fouled plugs. A plug that is carbon-fouled or has worn electrode gap increases the ignition demand on the magneto, causes misfires under load, and reduces power output. The standard replacement on Onan QG series generators is a Champion RC12YC or equivalent, gapped to specification for the specific model year.
Air filter condition is checked and replaced if loaded. In Florida's humid coastal air, paper air filters can absorb moisture and restrict airflow even when they do not look dirty from the outside. A restricted air filter richens the fuel mixture, accelerates carbon buildup in the combustion chamber, and reduces output power - the same symptoms owners often attribute to a failing carburetor. Air filter replacement is inexpensive enough that replacement on any filter with measurable restriction is standard practice on tune-up calls.
The Load Test - Why It Matters More Than the Oil Change
A generator that idles smoothly after a tune-up has demonstrated nothing about whether it will sustain the load your air conditioner puts on it during a Florida afternoon. The rooftop air conditioner on a typical Class A motorhome draws 12 to 16 amps at 120 volts during the compressor's running phase - roughly 1,400 to 1,900 watts - plus a starting surge of two to three times that figure when the compressor starts. A genset that is marginal in output voltage or frequency will run at idle but drop frequency under load, which causes the AC compressor to work harder, draw more current, and generate more heat than it is designed to handle.
The load test at Triton is done with the actual onboard air conditioner running at full cool, not with a portable resistive load bank. A resistive load is a fixed linear draw; a compressor motor is a reactive load with a power factor below 1.0 and a starting surge characteristic. Testing with the real load catches voltage sag and frequency droop that a resistive test would miss. The generator output is measured at the inverter/converter input and at the AC distribution panel, and both voltage and frequency are logged before and after the tune-up to document the improvement.
In practice, roughly one in four tune-up calls reveals a generator that passes no-load inspection but fails the full AC load test. The most common reason is a carburetor main jet that is partially restricted by varnish deposits - the generator idles normally because idle circuit fuel supply is adequate, but under the fuel demand of full load the restricted main jet cannot deliver enough fuel and the engine bogs, drops rpm, and the frequency falls from the nominal 60 Hz toward 55 or 52 Hz. That frequency drop causes the AC compressor to pull higher current, trips the genset's internal overload, or in some cases causes the compressor itself to trip its thermal protection. Owners who have experienced the generator shutting down on hot afternoons have usually experienced exactly this sequence.
Running at Low Load - Why It Causes Long-Term Damage
There is a widespread belief among RV owners that running the generator lightly - charging phones, powering a small fan, or running nothing at all - is a conservative, protective practice. The opposite is true, and understanding why changes how owners approach monthly exercise runs.
On gasoline generators, cylinder wall temperature during full-load operation is high enough to burn off oil that migrates past the piston rings. At no-load or very light load, cylinder wall temperature is lower, the rings seat less firmly, and a thin film of unburned oil and fuel residue builds up on the cylinder walls and in the exhaust port. Over time this residue carbonizes into hard deposits that score the cylinder walls, reduce compression, and cause hard starting. The condition progresses gradually and owners often attribute the declining performance to age when the actual cause is the habitual light-load exercise run.
Diesel generators have a more acute version of this problem called wet-stacking. At light load, diesel combustion temperatures are insufficient to fully combust the fuel, and unburned fuel and carbon accumulate in the exhaust manifold, turbocharger, and exhaust pipe. The visible symptom is black or grey oily residue at the exhaust outlet and a visible black smoke puff on startup. Wet-stacking does not clean itself at light load - it requires a sustained period of operation at 75 to 100 percent of rated load to raise combustion temperatures high enough to burn off the accumulated carbon. A diesel genset that has been exercise-run at no load for a season often requires a deliberate high-load purge run before it will perform reliably again.
The practical guidance for Florida owners is to run the monthly exercise session with the air conditioner on and at temperature setting that keeps the compressor cycling continuously for at least 30 minutes. That is the minimum load and duration to keep combustion temperatures in the range that prevents the problems described above.
Monthly Exercise Runs and Stale Fuel - Florida-Specific Guidance
Generator manufacturers universally recommend a monthly exercise run to prevent fuel varnishing in the carburetor, keep the brushes and slip rings on the alternator end from oxidizing, and ensure the starting battery remains charged. In Florida, monthly is the minimum - not a conservative interval but the actual floor below which fuel degradation becomes a service problem.
Ethanol-blend gasoline begins to degrade within 30 days in a hot environment without stabilizer. The ethanol component attracts water from humid Florida air through the fuel cap and vent line, and once the water content in the fuel reaches approximately 0.5 percent, phase separation occurs - the ethanol and water drop to the bottom of the bowl as a distinct layer, leaving denatured gasoline at the top. The carbureted small engine then draws from whichever layer the fuel pickup sits in. If it draws the water-alcohol phase, the engine will not start or will run so poorly it appears to have a major mechanical fault. If it draws the upper gasoline phase, it runs lean and without the octane contribution of the ethanol component.
Fuel stabilizer added to a fresh tank before storage delays this process for three to six months, depending on the stabilizer formulation and the storage temperature. Triton recommends a stabilizer rated specifically for ethanol blends - generic petroleum stabilizers are not formulated to prevent the hygroscopic action of ethanol and do not prevent phase separation as effectively as ethanol-specific products. Even with stabilizer, any stored fuel more than six months old in a Florida environment should be treated as suspect and the carburetor bowl drained before the first restart of the season.
Onan, Generac, Cummins, and Kohler - Platform Differences That Matter at Service
The Cummins Onan QG series - the most common genset in Class A and Class C motorhomes - has a specific service characteristic that surprises owners who have serviced small engines before. The oil fill is on the top of the unit, the oil drain is at the bottom and requires access through the generator door, and the fuel bowl drain is a separate fitting that is easy to overlook. The spec oil capacity for the QG 4000 is 1.1 quarts; overfilling by as little as a quarter quart can cause the engine to pump oil past the rings during operation, fouling the spark plug and triggering the low-oil shutdown in a confusing sequence where the oil is actually high, not low.
Generac's RV series generators - the QP and Marquis lines used in some fifth wheels and larger coaches - use a replaceable oil filter in addition to the standard service items. The filter thread direction is standard right-hand thread, but the filter housing is recessed in a way that requires a specific short-body filter wrench on many installations. Generac's recommended oil type for ambient temperatures above 50 degrees Fahrenheit is 10W-30 synthetic or 15W-40 conventional, and the company explicitly recommends synthetic for continuous-duty applications in hot environments - a recommendation worth following for Florida summer use.
Kohler RV generators, less common but still found on older coaches, use a points-and-condenser ignition system on some earlier models rather than the electronic ignition found on current Onan and Generac units. Points condition is checked at service because worn or corroded points cause the same hard-starting and no-load-only performance complaints as a fouled spark plug, but the diagnostic sequence is completely different. Knowing which ignition system is fitted before arriving at the coach avoids the situation of condemning a perfectly good carburetor based on symptoms that are actually ignition-related.
What the Oil Pressure Fault Means on an Onan - and What It Does Not Mean
The red oil pressure warning light on an Onan QG generator, or the "1" fault code that flashes from the primer button, tells you the engine's oil pressure sender is reading below threshold at startup or during operation. This is a protective shutdown - the engine cuts off before it runs with inadequate lubrication. But the fault does not necessarily mean the engine has low oil pressure; it means the sensor is reading low, and there are three distinct causes that require different responses.
First, the oil level may genuinely be low. Check the dipstick before doing anything else. If the level is low, add oil to the correct mark, attempt a restart, and log the interval since the last oil change. Engines that are consuming oil between services may have worn piston rings or a leaking oil seal - both conditions that show up as a pattern on service records and warrant a compression test to confirm.
Second, the oil pressure sender itself may have failed. The sender on Onan QG units is a simple pressure switch that completes a circuit at low pressure and opens it at normal pressure. The switch can fail in the closed position, causing the protective shutdown to activate even when oil pressure is normal. Replacing the sender is a straightforward service item - the sender is a common failure point on high-hour generators - and the diagnosis is confirmed by temporarily bypassing the sender circuit and observing whether the engine runs normally. Bypassing should only be done for the few seconds needed to confirm the diagnosis, not as a long-term solution.
Third, the engine may genuinely have low oil pressure due to wear in the oil pump or bearing clearances that have increased with high hours. This is the least common cause on generators with documented service histories, and the most common cause on generators that have not been serviced on schedule. A generator that shows repeated oil pressure faults after the oil level and sender have been verified warrants a teardown inspection before continued use.
Generator Tune-Up Pricing in Florida
| Service | Typical Range | Notes |
|---|---|---|
| Service call + tune-up (most makes) | $299 - $399 | Oil, filter, spark plug, and load test completed in first hour on most gensets |
| Basic tune-up (oil, filter, plug) only | $145 - $320 | Onan, Generac, Cummins, Kohler |
| Full annual service (tune-up + carb clean + load test) | $220 - $480 | Complete service; run test at full AC load included |
| Air filter replacement | $25 - $65 | Paper or foam; included in most tune-up calls |
| Fuel filter replacement | $35 - $95 | Inline or in-tank depending on model |
National average pricing shown for reference. Florida pricing may differ based on your location, coach type, and genset make and model. All prices are estimates only - final pricing is confirmed before any work begins.
Triton RV Repair provides mobile service across Florida. Travel charges may apply for locations outside primary service areas. Call (888) 702-6880 for a specific quote.
Frequently Asked Questions
How often should an RV generator be serviced in Florida?
Every 100 hours of run time or once a year, whichever comes first - and in Florida that interval should be treated as a hard ceiling rather than a suggestion. The combination of heat, humidity, and the ethanol content in pump gasoline degrades oil and fuel faster than the same clock time would in a cooler climate. Owners who use the generator heavily through summer often hit 100 hours before the calendar year is out.
What oil does an Onan generator take?
Most Onan QG and QD series generators specify 15W-40 or 10W-30 depending on ambient temperature range. In Florida, where ambient temperatures rarely drop below 50 degrees Fahrenheit even at night, 15W-40 is the standard choice for the QG 4000 and similar gasoline units. The exact specification is printed on the oil fill cap and in the operator manual. Capacity is typically one quart for smaller gasoline gensets and closer to two quarts for larger diesel units.
Why does my generator only run for a few seconds before shutting off?
The most common cause is a low-oil shutdown activation - the sensor cuts power to protect the engine before damage occurs. This happens when the oil level is low, when the genset is on a significant slope, or when the oil sender itself has failed and is sending a false low signal. A carburetor fault is the second most frequent cause: a partially blocked main jet starves the engine under any load. Less often the fault is a choke that failed to open fully after warm-up.
Is it bad to run the generator at low load?
Yes, and it is a more serious problem than most owners realize. On gasoline gensets, running below roughly 50 percent of rated load for extended periods allows carbon to build up on cylinder walls and exhaust ports, eventually causing hard starting and power loss. On diesel generators the same habit causes wet-stacking - unburned fuel accumulating in the exhaust and turbocharger. Both conditions require the generator to be run at full load to clear, and in severe cases mechanical service. The monthly exercise run should always include a real load - at minimum, the air conditioner.
How do I prepare my generator for storage if I am not using the RV for months?
The two priorities are fuel stabilizer and a final exercise run. Add a fuel stabilizer rated for ethanol-blend fuel to a full tank, run the generator at load for 20 minutes to circulate the treated fuel through the carburetor, then shut down. If the storage period exceeds three months, draining the carburetor bowl entirely is preferable to stabilized fuel, because even treated ethanol gasoline can degrade and leave varnish deposits over a long Florida summer. Change the oil before storage rather than after, since used oil contains combustion acids that corrode internal surfaces.
Sources and Further Reading
The service intervals and oil specifications cited on this page are drawn from published OEM documentation. For genset-specific part numbers and capacities, consult your operator manual directly.
Cummins Onan maintenance schedule - OEM service intervals, oil capacity specs, and tune-up part numbers for QG and QD series.
Generac generator manuals - Service interval guides and oil specifications for Generac QP and Marquis RV generators.