Quick answer
DG set maintenance is scheduled by running hours or calendar time, whichever comes first. Daily or pre-start checks cover fuel, oil, coolant, battery and leaks. Engine oil and oil filter changes are commonly scheduled every few hundred running hours, with fuel and air filters at the same or longer intervals, and coolant and major checks at higher hours or yearly. Exact intervals depend on the engine model, so follow the manufacturer's manual.
Why running hours matter
A DG set at a hospital may run hundreds of hours a month; one at a housing society may run only during power cuts. Servicing both on the same calendar would over-service one and neglect the other. Record the hour meter reading at every visit and plan the next service from it.
Low-use generators still need calendar-based care. Oil and fuel degrade, batteries discharge and seals dry out even when the engine sits idle.
Daily or pre-start checks (site operator)
| Task | Frequency | Notes |
|---|---|---|
| Fuel level | Daily / before start | Keep enough for the expected outage. |
| Engine oil level | Daily / before start | Check on the dipstick with the engine off and level. |
| Coolant level | Daily / before start | Check only when the engine is cool. |
| Visual check for leaks | Daily | Oil, fuel or coolant under the set. |
| Battery indicator / voltage | Daily | Weak battery is a top cause of failure to start. |
| Note hour meter reading | Daily or weekly | Write it in the log book. |
These checks are usually done by site staff. A good AMC provider trains them and supplies a simple log sheet.
Service by running hours
| Stage | Typical tasks | Notes |
|---|---|---|
| First service (new or overhauled engine) | Oil and filter change | Often earlier than the regular interval — check the manual. |
| Regular service (commonly a few hundred hours) | Engine oil, oil filter, fuel filter, clean air filter | Many small and medium sets fall in this band. Use the manufacturer's figure. |
| Next stage (roughly double the regular interval) | Above, plus air filter replacement, belt tension, coolant condition, valve clearance as specified | Intervals and tasks differ by engine model. |
| Higher-hour service | Above, plus coolant replacement, injector check, turbocharger check (if fitted), hoses | Often yearly for moderate-use sets. |
| Major overhaul | Top or major overhaul as per engine condition | Based on manufacturer guidance, oil analysis and performance. |
Yearly tasks (regardless of hours)
| Task | Frequency | Notes |
|---|---|---|
| Change engine oil and filters | If not done by hours in the year | Oil ages even without running. |
| Replace coolant | As per manual (often 1–2 years) | Use the specified coolant type and mix. |
| Battery health test | Yearly or more often | Load test; replace weak batteries before they fail. |
| Inspect hoses and belts | Yearly | Cracks, softness, glazing. |
| Check exhaust system | Yearly | Leaks, support, silencer condition. |
| Alternator and control panel check | Yearly | Terminals, insulation, AVR and protection settings. |
| Load test | Yearly or as agreed | Running on load reveals issues no-load runs miss. |
Monthly AMC visit checklist
| Task | Frequency | Notes |
|---|---|---|
| Review log book and hour meter | Every visit | Plan the next hour-based service. |
| Check fluids and leaks | Every visit | Oil, coolant, fuel; tighten fittings. |
| Clean or inspect air filter | Every visit | Dusty sites need more frequent attention. |
| Battery terminals and charger | Every visit | Clean terminals; check charging voltage. |
| Test run | Every visit | Start, run, check voltage, frequency and unusual noise. |
| Check ATS / AMF changeover (if fitted) | Every visit or monthly | Simulate mains failure as per site procedure. |
| Fuel tank water and sludge | Quarterly | Drain water separator; check tank bottom. |
Keep a proper log book
For each DG set, record: date, hour meter, work done, parts and consumables used, readings from the test run, and the next service due (by hours and by date). This is the basis for running-hour planning, and it protects you if the customer questions a service charge.
Writing DG AMCs
DG contracts often separate consumables (oil, filters, coolant) from repair parts, because consumption depends on running hours. State clearly which side each falls on — see comprehensive vs non-comprehensive AMC and the AMC contract format.
Generator service businesses can see how contracts and complaints are organised on our generator service management software page. More on AMC software and our AMC management software.
How AMCFlow helps
- Add each DG set as a unit under the customer, with its AMC start and end dates.
- Log a failure-to-start or breakdown as a complaint against the AMC, with a complaint number.
- Assign it to a technician, who gets a WhatsApp job alert with customer, mobile, address, product, problem and complaint number.
- Expiry dashboard shows DG contracts nearing expiry.
Frequently asked questions
How often should a DG set be serviced?
By running hours or calendar time, whichever comes first. Oil and filter changes are commonly scheduled every few hundred running hours, but the exact interval depends on the engine model.
What are the daily checks for a DG set?
Fuel level, engine oil level, coolant level, visible leaks, battery condition and the hour meter reading.
Does a generator need servicing if it rarely runs?
Yes. Oil and fuel degrade, batteries discharge and seals dry out even when the set is idle. Calendar-based servicing and regular test runs are needed.
Why is a load test important for a DG set?
Running on load shows problems that a no-load test run can hide, such as overheating, voltage drop or poor performance under demand.
Are oil and filters included in a DG AMC?
It depends on the contract. Many DG AMCs bill consumables like oil, filters and coolant separately because usage depends on running hours.