Diesel Generator Maintenance: A Practical AMC Checklist

A generator that only gets started up occasionally to "make sure it still works" is not the same as one under a proper maintenance contract. Backup power exists for the moment you actually need it — usually during a grid outage, often under real load — so the maintenance behind it matters more than for equipment that runs continuously and would show problems immediately. What a proper AMC visit should cover: - Engine: oil and filter condition, coolant level and condition, belts and hoses, air filter, fuel system and fuel quality (contaminated or old diesel is a common cause of failure-to-start). - Alternator: winding condition, connections, output voltage and frequency under test load. - Controller: fault log review, battery and charging system condition (a dead start battery is one of the most common real-world generator failures), automatic transfer switch (ATS) function test. - Load test, not just a no-load start: starting a generator with no load connected can mask problems that only appear once real load is applied — a proper visit should include a test under load where practically possible, not just confirm the engine turns over. - Canopy/enclosure: ventilation, sound attenuation condition, general housekeeping and pest/rodent checks (rodent damage to wiring is a genuinely common failure cause in unused enclosures). - Fuel storage: tank condition, water/contamination check, fuel quantity against expected runtime. Why "it started fine last time we tested it" isn't the same as "it will start when the grid actually goes down." A generator sitting idle between real outages needs its battery, fuel and engine condition actively maintained — none of that happens by itself, and problems (a weakening battery, degrading fuel, a stuck relay) often only surface at the worst possible moment: an actual outage. How often: for standby generators (used only during outages), a maintenance visit every 3-6 months is a reasonable baseline, with more frequent checks for larger, business-critical installations (see our generator capacity guide for how tier affects criticality) and generators in humid, coastal or dusty environments. For generators running more regularly (prime/continuous duty), servicing intervals should follow the engine manufacturer's running-hours schedule rather than a fixed calendar period. We provide AMC-based maintenance covering this full scope for generators we supplied as well as existing third-party installations. Get in touch to set up a schedule matched to your generator's tier and actual usage pattern.