Generator Runs, Then Shuts Down
The engine starts, sounds fine, powers the house for a while — and then quits on its own, sometimes within a minute, sometimes hours in. This isn't a starting problem; it's almost always a protective sensor doing exactly what it's designed to do. How long it ran before cutting out is the single biggest clue to which sensor tripped.
What this looks like
Group the timing into three rough buckets. Seconds to about a minute: most consistent with a low-oil-pressure shutdown or a lost RPM/timing signal — the engine caught, ran just long enough for the controller to confirm it, then the safety switch closed or the signal dropped out. Minutes under real load: more consistent with overload, undervoltage, or underspeed — the engine was fine at idle but couldn't hold up once the house's actual demand hit it, especially when a well pump or central AC kicks on. An hour or more, especially in hot weather or with restricted airflow: points toward a genuine overheating shutdown, since it takes real running time for coolant or air-cooled engine temperatures to climb into unsafe territory. All three brands documented here report these as distinct faults rather than one generic "shutdown" message, which is what makes the timing worth paying attention to before you even open the enclosure.
Most likely causes, ranked
- Low oil pressure. The single fastest-tripping shutdown on this list — oil level below the safe mark, overdue oil, or a failed pressure switch will often shut an engine down within the first minute of running.
- Overheating. Blocked intake or exhaust vents, debris packed around the enclosure, low coolant on liquid-cooled models, or running at rated load in high ambient heat — this one builds over real running time rather than tripping instantly.
- Output voltage or frequency out of range under load. An overloaded circuit, a large motor starting under load, or a failing voltage regulator can pull output outside the safe band once the house is actually drawing power, even though the generator seemed fine unloaded.
- Lost RPM/timing signal. Less common but serious — the engine may sound like it's running fine right up until the controller loses its confirmation signal and cuts it, which usually points to the speed sensor itself rather than the engine.
Which fault codes match this
| Cause category | Generac | Kohler | Briggs & Stratton |
|---|---|---|---|
| Low oil pressure | 1300 | Engine Oil Pressure Low | FC_2 |
| Overheating | 1400 | High Engine Temperature / Low Coolant Level | FC_7 |
| Voltage / frequency out of range | 1900 / 1800 / 2100 | Voltage Low / Voltage High / EngineSpeed Low | FC_3 / FC_5 |
| Lost RPM/timing signal | 1501/1505/1511/1515 | — | — |
What you can check yourself
- Time how long it ran before shutting down — under a minute versus a longer, load-dependent run tells you which section of the table above to start with.
- Once cool, check oil level on the dipstick and top off with the grade listed on the data plate; this rules out the fastest-tripping cause first.
- Clear leaves, snow, or debris from intake and exhaust vents, and confirm the unit has its specified clearance from walls or structures.
- On liquid-cooled models, check coolant level only once the system is fully cooled — never open a hot cooling system.
- Note what was running in the house when it cut out; if a well pump or AC unit had just kicked on, that points at load rather than a mechanical fault.
More help
If you already have the exact code from the panel or LED, the code lookup is faster than this page. Otherwise browse by brand: Generac, Kohler, or Briggs & Stratton.