Cummins Onan Generator Repair & Service

Factory Authorized Service Center

Your Onan generator isn't something most RV shops can properly diagnose. These units integrate fuel systems, ignition timing, voltage regulation, and electronic controls that require factory training and diagnostic tools to service correctly. 3R RV Service Center is Factory Authorized by Cummins to service all Onan RV generators - and we've been doing it for over 20 years.

Why Your Onan Needs Professional Service:

Onan generators are not lawnmower engines with an alternator bolted on. They're precision power plants designed to produce clean, stable AC power for sensitive RV electronics. The fuel system, ignition system, governor, and voltage regulation all work together - when one component drifts out of spec, it affects everything else.

Most shops will tell you one of three things: "We don't work on generators," "Call Cummins," or they'll replace the carburetor and hope for the best.

We don't guess. We're factory trained on these systems and diagnose them properly the first time.

Service Schedule - What Your Onan Actually Needs:

Every 2 Weeks (Owner Responsibility): Run the generator under load for 2 hours minimum to prevent fuel system issues and carbon buildup. Generators that sit unused develop gummed carburetors, stuck valves, and stale fuel problems. Check oil level before each use.

Every 150 Hours or Annually (whichever comes first): Change engine oil and filter. Replace or clean air filter. Inspect spark plug (gas units) or glow plug (diesel units). Check spark arrestor screen. Inspect fuel filter. Check battery and charging system. Test output voltage and frequency under load. Inspect exhaust system for leaks.

Every 500 Hours or 2 Years: Replace spark plug (gas units). Replace fuel filter. Clean or rebuild carburetor (gas units). Inspect governor linkage and adjustment. Test voltage regulator output. Load bank test at rated capacity. Full electrical system inspection.

Every 1000 Hours or 4 Years: Valve adjustment check. Injector service (diesel units). Comprehensive ignition system service. Control board diagnostic. Full system calibration.

As Needed: Carburetor rebuild or replacement. Fuel system cleaning after storage. Winterization before extended storage. Exercise cycle programming.

What Happens When Service Is Neglected:

We see the same failures every year from owners who let their generators sit unused or skipped maintenance:

Gummed carburetors - The number one generator killer. Fuel left in the carburetor turns to varnish and plugs jets and passages. What should have been a $200 service becomes a $400-600 carburetor replacement.

Stale fuel damage - Old gasoline breaks down and leaves deposits throughout the fuel system. We've seen fuel pumps, fuel lines, and tanks damaged by fuel that sat too long.

Carbon buildup - Generators run under light loads develop carbon on valves and in the combustion chamber. This causes hard starting, rough running, and eventually valve damage.

Stuck exhaust valves - Common on generators that sit for months. The valve seizes in the guide and the engine won't start or runs on one cylinder.

Failed voltage regulators - Voltage spikes from improper loading or age damage the regulator. This can also damage your RV's electronics and appliances.

Dead start batteries - The generator charges its own start battery during operation. Generators that sit unused end up with dead batteries that won't hold a charge.

Control board failures - Moisture, rodents, and vibration damage control boards over time. We see chewed wiring and corroded connections regularly.

Seized components - Generators stored without proper preparation develop seized governors, stuck chokes, and frozen fuel solenoids.

Models We Service:

Cummins Onan - All current and legacy RV generators:

Current Production Gas/LP: QG 2500 LP (2.5kW), QG 2800 (2.8kW gasoline), QG 3600 LP (3.6kW), QG 4000 (4.0kW gasoline), QG 5500 LP (5.5kW), QG 7000 (7.0kW gasoline)

Current Production Diesel: QD 3200 (3.2kW), QD 5000 (5.0kW), QD 6000 (6.0kW), QD 8000 (8.0kW), QD 10000 (10.0kW), QD 12500 (12.5kW)

Legacy Models: MicroLite (all KY series), MicroQuiet (all KYD series), Marquis Gold (BGM, NHM series), Marquis Platinum, Emerald Plus (BGE, NHE series), Emerald GenSet, All BGD and NHD diesel models

Components We Service and Repair:

Fuel System (Gas/LP): Carburetor (rebuild and replacement), Fuel pump and fuel solenoid, Fuel filter and sediment bowl, Choke assembly and linkage, Governor and throttle linkage, LP regulator and lock-off, Fuel lines and fittings, Primer system

Fuel System (Diesel): Fuel injection pump, Injectors and injector lines, Fuel transfer pump, Fuel filter and water separator, Glow plugs and glow plug controller, Fuel solenoid, Governor

Ignition System: Spark plugs, Ignition coil and module, Points and condenser (legacy units), Electronic ignition conversion, Flywheel and magnets, Kill switch and safety circuits

Electrical and Controls: Voltage regulator (AVR), Control board and PCB, Hour meter, Start/stop switch and remote panel, Circuit breakers, Brushes and slip rings, Stator and rotor, Rectifier assembly, Battery charging circuit

Air and Exhaust: Air filter and housing, Exhaust manifold and muffler, Spark arrestor screen, Exhaust flex pipe, Generator enclosure and mounts

Engine: Oil pump and pressure switch, Valve

adjustment, Cylinder head and gaskets, Piston rings and bearings, Crankshaft seals, Starter motor, Cooling fins and shroud

Common Problems We Fix:

Generator won't start - Could be fuel delivery, ignition, compression, or control board. We diagnose the actual cause before replacing parts.

Starts then shuts down immediately - Often low oil pressure shutdown, fuel starvation, or control board fault. Requires proper diagnosis.

Runs but won't take load - Typically carburetor, governor, or voltage regulator issues. We load test to verify output.

Surging or hunting - Governor out of adjustment, carburetor issues, or air leak. We adjust to factory specs.

Low power output - Could be voltage regulator, brushes, or internal alternator issues. We test output under load at multiple points.

Fault codes on control panel - We have factory diagnostic capability to read and clear codes and identify the actual failure.

Excessive fuel consumption - Usually running too rich from carburetor issues or governor problems. We tune for efficiency and proper operation.

Generator runs rough - Carbon buildup, valve issues, ignition problems, or fuel quality. We diagnose before we recommend repairs.

No AC output but engine runs - Voltage regulator, brushes, circuit breaker, or internal alternator failure. Requires electrical diagnosis.

Overheating and shutdown - Blocked cooling air, failed cooling fan, or excessive load. We check operating temps under load.

What To Expect:

We diagnose the actual problem before recommending repairs. Onan generators are precision equipment and we're not going to sell you a new carburetor when you need a $15 fuel solenoid. Every repair is inspected by an RVTI Level 4 Master Technician before your rig leaves.

If your generator needs parts we don't stock, we'll give you an honest timeline. Cummins keeps most parts available, but some legacy components require longer lead times.

Contact:

Stop chasing shops that can't help you. Call 3R RV Service Center at (636) 583-2244 or stop by our facility at 7819 Highway 47, Union, Missouri 63084. We're open Monday through Friday 8am-6pm and Saturday 8am-12pm.