Generator engine-speed sensing lets the controller verify cranking and running RPM. Related symptoms include RPM loss, under/overspeed or unexpected shutdown. Those symptoms do not prove the component failed: separate no-start from loaded shutdown and preserve history. Check the fuel supply and the external shutoff before anything else.
What this covers
- electronically controlled generators
What it does not cover
Differential
Likely causes of “Generator engine-speed sensing”, and how to tell them apart
- 1
The generator is out of fuel or the supply is low
What separates it The engine speed falls and the unit shuts down with an underspeed or RPM alarm, and the LP tank or gas supply is low.
How to confirm Check the fuel supply and the external shutoff before anything else.
- 2
Overload or a large starting load pulls the speed down
What separates it The alarm appears when a big load such as an air conditioner starts and the unit is otherwise fine.
How to confirm Remove large loads and see whether the alarm returns unloaded.
- 3
Maintenance is overdue: air filter, spark plugs or oil
What separates it The generator has not been serviced for years and its speed is unstable.
How to confirm Check the last service date and the air filter condition.
- 4
The speed sensor or its wiring is faulty
What separates it The alarm appears at start-up with no load and correct fuel, and the history shows a sensor code.
How to confirm This needs an authorized service technician to test the sensor.
Before you touch a setting
Record this first — changing settings destroys the evidence
- The alarm code, whether it appears at start or under load and the controller history.
- The fuel level, the last service date and the load at the time.
- Whether it fails in the weekly exercise or only in an outage.
Try in this order
0 of 2 completedTest before you replace
ReversibleSeparate no-start from loaded shutdown and preserve history.
Weigh the repair
ReversibleReplacement difficulty for the generator engine-speed sensing is authorized service after battery, load, fuel, airflow and maintenance.
Stop boundary
When this stops being a self-service repair
- !Preserve the alarm history before clearing anything, and leave sensor testing to authorized service.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does the engine-speed sensor do?+
It tells the controller how fast the engine is turning so it can confirm cranking, running speed and an over- or under-speed condition.
What does speed sensing do?+
It tells the controller how fast the engine is turning so it can regulate output and shut down if speed is wrong.
What are the signs of a fault?+
Hunting or surging, failure to reach speed, or shutdown codes about speed.
Is it a home repair?+
Usually a technician's job, because other causes such as fuel or air need ruling out first.