Generac codes 1500–1522: RPM sensor loss

Record whether the alarm appeared when starting or after the unit had been running, whether it was an outage or an exercise cycle, the loads on the generator, the fuel type, the LP level and any battery message.

If it failed to start: check the battery, battery terminals and cables. On a Guardian controller a CHECK BATTERY message means have the battery tested and replaced if needed, since home standby batteries last 3 to 5 years on average. If the battery is above 12.6 volts, look for corrosion and loose terminals, and note that a voltage reading only shows voltage is present, so a load test is needed to confirm condition. Verify the fuel shutoff valve is ON, that the fuel selection and jet orientation match the fuel source, and on LP that the level is not below 30 percent.

Check the air filter and the maintenance schedule. If it shut down while running, Generac says a weak battery or bad connection is likely not the cause: look for an overload or a sudden large load change, such as an air conditioner, heater or pump starting or stopping.

Correct an obvious battery, fuel-level, airflow or maintenance problem, then clear the alarm once: on an Evolution controller press OFF, ENTER twice, then AUTO, and on a Power Zone 200 controller hold OFF for 3 seconds. Fuel pressure and fuel quality checks need specialized equipment and must be done by a professional, after the simpler causes are ruled out.

Test with the loads removed and restore household loads one at a time only under Generac's outage procedure. Never start a generator while it is under load.