In brief
- Most standby generator failures come from a small number of causes: a flat battery, poor fuel, low coolant or a control switch left out of “auto”.
- A short weekly inspection and a monthly test run catch most of these before an outage does.
- Oil, filters, coolant and belts are changed at the intervals in the manufacturer’s manual, by running hours or by time, whichever comes first.
- A yearly full service with a load bank test proves that the generator can carry its rated load.
Why do standby generators fail when they are needed?
A standby generator may run for only a few hours a year. Long idle periods are hard on it. The starting battery loses charge, diesel takes on water and grows sludge, rubber hoses and belts harden, and coolant loses its protective additives. None of this shows until the mains fails and the set is asked to start.
Routine checks are how a facility manager finds these faults on an ordinary weekday instead of during an outage.
Which checks should be done, and how often?
Use the table below as a starting point. The manufacturer’s manual for your generator takes priority, and sets that run daily need servicing more often than standby sets.
| How often | What to check or do |
|---|---|
| Every week | Walk round the set and look for oil, fuel or coolant leaks. Check fuel, oil and coolant levels. Confirm that the battery charger is working and that the control panel is in “auto” with no alarms. Keep the area clean and the air inlets clear. |
| Every month | Run the generator, under load where possible, until it reaches working temperature. Record voltage, frequency, oil pressure and temperature. Check battery terminals, belts and hoses. Drain water from the fuel filter or water separator. |
| Every six months, or at the running hours in the manual | Change engine oil and the oil filter. Change fuel filters and check the air filter. Check coolant condition and belt tension. Test the automatic transfer switch. Check electrical connections and the alternator. |
| Every year | Carry out a full service. Run a load bank test. Test the fuel and clean the tank if needed. Test or replace coolant as the manual requires. Test the protective shutdowns and review the year’s service log. |
Which checks can your own staff do?
The weekly inspection needs no tools and takes about ten minutes. A caretaker, guard or technician can do it with a printed checklist. The monthly test run can also be done in-house once staff have been shown the procedure and the safe operating limits.
Leave oil and filter changes, fuel system work, electrical testing, transfer switch testing and load bank testing to a qualified generator technician. These tasks involve hot fluids, moving parts and live electrical equipment.
What should the generator log record?
Keep a logbook at the generator. For every check or run, record:
- The date and the name of the person.
- The running-hours reading.
- Fuel, oil and coolant levels.
- Voltage, frequency, oil pressure and temperature during the run.
- Anything unusual seen, heard or smelled.
- Work done and parts replaced.
A log makes trends visible. Falling battery voltage or rising engine temperature shows up in the figures weeks before it causes a failure. The log also supports warranty claims and audits.
What are the warning signs between services?
- The engine is slow to start or needs several attempts.
- Black, white or blue smoke continues after the engine has warmed up.
- There is a new noise or vibration.
- Oil, fuel or coolant appears on or under the set.
- Voltage or frequency drifts, or the lights flicker when the generator is running.
- Fuel consumption rises without a change in load.
- An alarm appears on the control panel, even if it clears.
Report any of these to your service provider before the next outage.
How does load affect the health of a generator?
A diesel engine is healthiest when it works. A set that runs for long periods at a small fraction of its rating does not get hot enough to burn its fuel cleanly. Unburnt fuel and carbon then build up in the engine and exhaust, a condition known as wet stacking. Test runs under a meaningful load, and a yearly load bank test, keep the engine clean and prove that it can deliver its rated output.
Overloading is the opposite problem. If the site has grown since the generator was installed, ask for the load to be measured.
How should fuel be looked after?
Fuel problems are among the most common causes of generator faults. Keep the tank reasonably full to limit condensation. Drain water from the tank and the water separator regularly. Buy diesel from a reliable source and keep the storage clean and sealed. Fuel that has been stored for a long time should be tested, and cleaned or replaced if it has degraded.
When should you call a generator technician?
Call a technician when a warning sign appears, when the generator fails a test run, when a service is due by hours or by date, and after any long run during an extended outage. An older set, or one with an uncertain history, benefits from a generator health audit, which reports on its condition and the work it needs.
How can Vulfem International help?
Vulfem International repairs, services and maintains diesel generators for institutions, businesses and homes across Kenya. Its services include preventive maintenance contracts, engine diagnostics, corrective repairs, load bank testing, fuel and cooling system servicing and generator health audits. Read more on the Generator Repair, Service and Maintenance page.
Get a personalised quote
Each service or maintenance contract is quoted after a review of the generator. Message Vulfem International on WhatsApp at +254 739 629 118 or email fmugo@vulfem.com. Generator down? Call +254 739 629 118.
Last updated: 5 October 2026.
