San Diego RV Center has handled RV generator repair in San Diego since 1990, working on Onan, Cummins, and Generac units installed in Class A, B, and C motorhomes as well as larger fifth wheels. If your generator won’t start, runs rough, shuts off under load, or hasn’t been serviced in years, we diagnose and repair it at our El Cajon shop — with a 90-day warranty on parts and labor.

How RV Generators Fail

Most RV generator failures come down to one of three things: fuel problems, maintenance that’s been skipped too long, or a component that’s reached the end of its life. Onan generators — the most common brand in motorhomes — are reliable machines, but they need regular oil changes, fresh fuel, and spark plug replacements on schedule. When those services get pushed back, the generator pays for it.

The other common failure point is the fuel system. RVs that sit between trips for months at a time end up with stale fuel and gummed carburetors. The generator cranks but won’t run, or runs for a few minutes and quits. That’s a carburetor cleaning job, not a replacement — but only if it’s caught early enough.

RV Generator Services We Perform

• Generator diagnostics: Full assessment of why the generator won’t start, runs rough, or shuts off under load
• Fuel system cleaning: Carburetor cleaning and fuel line service for generators that have sat idle
• Oil and filter changes: Generator-specific oil service to manufacturer specifications
• Spark plug replacement: Replacing worn plugs that cause hard starting or misfires
• Load testing: Running the generator under realistic electrical load to confirm it holds output voltage and doesn’t shut down
• Control board and voltage regulator repair: Diagnosing and replacing failed electronic components
• Generator replacement: Full removal and installation when the unit is beyond economical repair

Generator work often surfaces related electrical issues in the coach. If we find something during the generator repair, we’ll flag it before it becomes a bigger problem. Our general RV repair services page covers the full scope of what we handle at the shop.

Brands We Service: Onan, Cummins, and Generac

Onan (a Cummins brand) is the generator found in most Class A and Class C motorhomes built in the last 30 years. We service the full Onan lineup, including the QD, QG, and MicroQuiet series. Cummins commercial generators and Generac units are also in our wheelhouse.

If your generator brand isn’t listed here, call us. We’ve worked on enough variety over 36 years that we’re unlikely to turn away a job just because it’s not an Onan. Reach us at (619) 561-3531 and describe what you’ve got.

Generator Maintenance vs. Generator Repair

There’s a practical difference between a generator that’s broken and one that just needs maintenance. If your generator starts and runs fine under light load but shuts off when you run the air conditioner, that’s often a load capacity or fuel delivery issue — a repair job. If it’s been two years since the last oil change and it’s running rough, that might be a maintenance job.

We’ll tell you which one you’re dealing with after the diagnostic. Connecting generator maintenance to your broader RV upkeep is smart — our RV motorhome maintenance service covers everything from fluid checks to systems inspections so nothing gets missed between trips.

When to Replace Instead of Repair

A generator replacement makes sense when the repair cost approaches or exceeds the value of the unit, or when multiple systems — the control board, the alternator winding, and the carburetor — have failed at the same time. We’ll give you an honest assessment of whether repair or replacement is the better path.

Replacement generators are installed to manufacturer specs with proper mounting, exhaust routing, and electrical connections. We also test the new unit under load before the rig leaves the shop. For context on how RV electrical and generator systems connect, our blog post on causes of RV electrical issues is worth a read.

90-Day Warranty on Generator Work

All generator repairs and replacements at San Diego RV Center come with a 90-day warranty on parts and labor. We stand behind our work, and since we’re a fixed shop in El Cajon — not a mobile service or a chain — you know exactly where to come back if there’s ever an issue.

We also back this up with a track record. See our why choose San Diego RV Center page if you want to understand how we operate before you drop off your rig.

Frequently Asked Questions

Why does my RV generator start but shut off after a few minutes?

This is usually a fuel delivery problem — a dirty carburetor, clogged fuel filter, or stale fuel that can’t sustain the engine under load. It can also be caused by a low oil shutoff triggering if the oil level is borderline. We diagnose this during our standard generator assessment.

How often should I service my RV generator?

Onan recommends oil changes every 150 hours of operation or once a year, whichever comes first. Spark plugs typically need replacing every 500 hours. If your rig sits for long periods, an annual service before the camping season is a good habit regardless of hours.

Can you replace my generator with a different brand or size?

In many cases, yes. The replacement needs to fit the existing compartment, match the fuel type (gasoline, diesel, or propane), and meet the electrical load requirements of your coach. We’ll assess the options and walk you through the tradeoffs before any work is approved.

Do you service generators for both motorhomes and towable RVs?

Yes. Generators are most common in motorhomes, but some fifth wheels and larger travel trailers have them too. Bring it in regardless of rig type and we’ll take a look. You can also check our RV repair FAQs for more common questions about our services.