A standby generator that won't start has usually been telling you something for weeks — a missed weekly exercise, a fault light you didn't notice, a battery quietly aging out. Here's how to read those signs, what you can safely check yourself, and when to stop and call a professional.
Get Free Generator Repair & Service QuotesLike a car battery, a generator battery ages out, and it is the single most frequent reason a standby unit won't fire. If your unit is a few years old and the battery has never been replaced, that is the first thing a technician will test. Look for the battery's age if it's marked, and note whether the unit has been slow to crank on recent exercises — but leave battery replacement and load testing to a technician if you're not comfortable working around the unit's electrical components.
The controller display usually says what's wrong: a fault light, an error code, or a message about low oil, low coolant, or a failed exercise. Write down exactly what it shows, including any code — that note is the most useful thing you can hand a technician, and it often turns a long diagnostic visit into a short one. Don't clear codes repeatedly to make the light go away; a latched fault is information, not an annoyance.
Is the unit switched to AUTO rather than OFF? Has the weekly exercise actually been running — listen for it, or check the exercise schedule on the controller? Is the area around the unit clear of debris, snow, and stored items blocking airflow? On propane, is there fuel in the tank? These checks cost nothing and rule out the embarrassing causes. Anything involving the fuel line, gas pressure, or opening electrical enclosures is a professional's job, not a homeowner check.
Call promptly if the unit failed during a real outage, if it cranks but won't catch, if it starts then shuts down, if you smell fuel, or if a fault returns after being cleared. Mid-storm is the worst time to discover a dead generator — every technician in the county is booked — so a failure on a calm week is the cheapest version of this problem you'll ever have.
Standby generators sit idle for months, and idle time is hard on batteries and fuel systems. A battery that was marginal last season often fails over a winter, and a missed exercise cycle can let a small fault go unnoticed until the night you need the unit. Annual maintenance exists precisely to catch this drift.
Don't improvise. Standby units have their own charging and control systems, and incorrect jump procedures can damage the controller. If the battery is the problem, a technician can test it properly and replace it with the correct type — it's usually one of the more affordable repairs.
Yes — treat it as an early warning, not a minor glitch. The exercise cycle is how the unit proves it can start, and a stopped cycle often means a fault, a dead battery, or a controller problem. Get it checked before the next storm, not during it.
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