Onan generator repair and service
Onan is a Cummins brand, and the sets carrying the name here are almost all compact diesel gensets built into places nobody left room to work in — under a yacht's cockpit sole, in a machinery space, or on a vehicle-mounted installation. That constraint, not the badge, is what shapes the job.
We hold no Onan or Cummins dealership
No dealership, no service appointment and no manufacturer accreditation — the names on this page identify equipment we service, nothing more. On an out-of-warranty compact set that independence is usually the more useful thing to be: a dealer's incentive is to supply the part, ours is to measure whether you need one. If the set is still inside its manufacturer warranty, use the authorised network for repair work.
Established 2011, over 25 years of experience, working from the workshop behind Yerevan Steel Factory in Industrial Area 15, Sharjah. Because these sets are so often afloat, most of what follows also applies on marine and boat generator repair.
Why a compact set is its own job
Access governs everything
On a large standby set you decide what to do and then do it. On an Onan set you decide what is physically reachable, and the plan follows from that.
The sound shield comes off first
Nothing can be seen until it does — and in many installations it will not come off in one piece.
It is cooled by raw water
Heat exchanger, not radiator. The fault list runs through sea cock, strainer, impeller, tube stack and wet exhaust before it reaches the engine.
The engine plate governs, not the badge
The engine is a small industrial diesel, commonly a bought-in unit rather than a Cummins engine. It sets the service schedule and the parts.
Confined installations age hardware
Vibration, corrosion and heat wear wiring, mounts, hoses and exhaust components faster than the same set would age on a bench.
Removing a compact set for workshop work often means dismantling more of the installation than the repair itself. That decision is worth making before anything is unbolted, not halfway through.
Two lists
What we are called to, and what we do about it
Cooling and raw water
- Overheating and high-temperature shutdown — raw water flow, impeller, tube stack, thermostat
- No raw water at the exhaust
- Wet exhaust components corroded through
Starting and output
- Will not start, or starts and stops — batteries, fuel supply, water in the fuel, or a latched shutdown that has to be read before it is reset
- No output or unstable voltage with the engine running — excitation, AVR, diodes or windings
- Salt and damp corrosion at the terminal box, control connections and harness, producing intermittent faults that look electronic and are chemical
Engine and installation
- Smoke, blow-by and oil consumption on a high-hour set
- Vibration, mount and exhaust failures in a confined installation
What we do
- Diagnosis on board or ashore
- Raw water work — impeller, pump, heat exchanger cleaning and pressure testing, thermostat, anodes, wet exhaust components
- Servicing to the engine manufacturer's own schedule, readings logged, written report
- Alternator testing, insulation resistance, drying and rewinding in our own winding bay
- AVR and control diagnosis
- Fuel system work, with injection equipment tested and calibrated on our own benches
- Engine overhaul with the heavy machining done in our own shop rather than sub-contracted
Where the set has to come out, the removal, the workshop work and the refit can be sequenced around a docking or a sailing date. Give us the dates at enquiry stage.
Parts
Not tied to a supply channel
Parts are quoted genuine where you want them or the application demands it, and quality aftermarket where that is sensible — and the quotation says which is which. On a compact set the sourcing question is usually answered by the engine plate rather than the set badge, which is why the first thing we ask for is a photograph of it.
- Photograph the engine plate
It tells us the engine family, the service intervals and the parts route in one frame.
- Photograph the access
How much space there is around the set decides more of the plan than the fault does.
- Tell us marine or mobile
The raw water side and the vibration picture differ, and so does the parts list we bring.
Common questions
Onan sets, answered
Are you an authorised Onan or Cummins dealer?
No. We hold no dealership or service appointment with either. We are an independent workshop, and we state that rather than let it be assumed.
Is an Onan generator a Cummins?
Onan is a Cummins brand. The engine inside a compact Onan set is frequently a bought-in industrial diesel rather than a Cummins engine, so parts and service intervals follow the engine data plate rather than the badge on the shield.
My Onan set overheats within minutes of starting.
Raw water flow, in this order: sea cock, strainer, impeller, heat exchanger, thermostat. If the impeller has shed vanes, they are downstream in the tube stack and have to be recovered — see generator overheating.
Can you work on the set in place, or does it have to come out?
Whichever the installation allows. A good deal can be done in place; alternator rewinding and engine machining cannot, because those machines do not travel. We tell you which applies before anything is dismantled.
Do you repair petrol Onan sets?
No. Our work is diesel.
Send us a photograph of the plate
The engine and set data plates, whether the installation is marine or mobile, and the fault. Access photographs help more than most people expect on this kind of set. Open 7 days, 07:00–20:00.