• If this menu states CHECK BATTERY, have the battery tested and replace if needed. Home standby generator batteries last 3-5 years on average.
• For help, reach out to a local service dealer: How Can I Find a Generac Service Dealer in My Area?
• If you feel comfortable, you can test and replace the battery yourself: How can I test if my home standby battery is still good (multimeter test)?
• To replace the battery: How do I replace the battery on my home standby generator?
• If the battery voltage is greater than 12.6 volts, check that the battery cables and battery terminals are free of corrosion and are properly secured: How Do I Inspect the Battery On My Home Standby Generator?

Note: Testing battery voltage only indicates that voltage is present. To verify the battery is in good condition, it requires load testing. This can be done at many auto parts stores. 

• Verify that the fuel shutoff valve is open (ON).
• If the valve is closed (OFF), fuel cannot reach the unit, preventing it from starting. 

The unit is capable of operating on Natural Gas (NG) or Liquid Propane (LP), and is set manually during installation in two places:

• Controller menu settings: The controller should be set to match the fuel source being used.
  • How do I verify the correct fuel selection is selected for my generator?
• Fuel jet orientation: For some generator models, the fuel jets must be physically oriented to the correct fuel type. 

Note: For Next Generation Air-Cooled Standby series generators, fuel selection is performed in the Field Pro app during initial setup prior to first startup using the guided setup process, or in the generator configuration settings. This is done by your installer. See: How Do I Commission a Generator in the Field Pro Application?

Both the controller fuel selection and the fuel jet orientation must match the fuel source being used. 

Note: If your unit was not recently installed, it is unlikely that these settings are incorrect. However, verifying them is still considered best practice to rule out a potentially user-resolvable issue. 

If your unit is supplied by LP, check the fuel levels. 

• When LP levels drop below 30%, fuel pressure may be affected, which can trigger an RPM sense loss alarm. 

Natural gas grids can be impacted during major outage events or construction. Contact your natural gas supplier to verify any known issues in your area. 

Note: Most natural gas suppliers post outage or supply disruption alerts on their websites. 

Sometimes, checking user-serviceable components and performing recommended maintenance can resolve RPM sense loss issues. 

• Check the condition of the air filter. Blocked or restricted airflow can affect engine performance and lead to an RPM sense loss alarm. See: How Do I Check and Change the Air Filter On My Home Standby Generator?
• Verify maintenance items have been completed per the maintenance schedule: Where Can I Find the Maintenance Schedule for My Generac Home Standby Generator?

• Improper fuel pressure or dirty/poor quality fuel can contribute and/or prevent the unit from starting. However, due to the specialized equipment and safety considerations involved, fuel pressure and fuel quality checks must be performed by a professional. 
• Before considering fuel pressure or fuel quality, it's important to follow a systematic diagnostic process with a Generac IASD. Think of this like checking a low tire—before replacing it, you would first check the air pressure and see if it holds air. Similarly, fuel pressure or fuel quality issues should only be evaluated after ruling out other common causes outlined above.
• If all other troubleshooting checks do not resolve the issue, work with your dealer to determine whether contacting your gas supplier to verify fuel pressure or fuel quality is the next logical step in the troubleshooting process. 

• Your unit relies on stable and consistent operation to produce electricity properly. A sudden increase or decrease in a large electrical demand can interfere with the unit's function and lead to unexpected errors and shutdowns. 
• Motorized electrical appliances, (e.g., AC units) have a starting wattage that may be 3-4 times the running wattage. If multiple appliances all try to come on at the same time, such as in an outage situation, this can overload the generator. 
  • If the generator is properly sized or utilizes a load management system overload risks should be mitigated. 
• See: What Happens if the Generator Gets Overloaded?

• If you utilize any load management systems, verify they work as expected. (Generac Load Manager, Smart AC Module)
  • What Is an Integrated Smart Air Conditioning Module (SACM)?
  • What is a Generac Load Manager (previously known as a Smart Management Module (SMM))?
• If the issue appears to be load related, remove non-essential loads and attempt to start and run the unit with no load to verify if the issue may be load related.
• Identify and prioritize critical loads, then gradually add others to isolate any problematic loads. 

The unit is capable of operating on Natural Gas (NG) or Liquid Propane (LP), and set manually during installation in two places:

• Controller menu settings: The controller should be set to match the fuel source being used.
  • How do I verify the correct fuel selection is selected for my generator?
• Fuel jet orientation: The fuel jets must be physically oriented to the correct fuel type. 

Note: For Next Generation Air-Cooled Standby series generators, fuel selection is performed in the Field Pro app during initial setup prior to first startup using the guided setup process, or in the generator configuration settings. 

Both the controller fuel selection and the fuel jet orientation must match the fuel source being used. 

Note: If your unit was not recently installed, it is unlikely that these settings are incorrect. However, verifying them is still considered best practice to rule out a potentially user-resolvable issue. 

If your unit is supplied by LP, check the fuel levels. 

• When LP levels drop below 30%, fuel pressure may be affected, which can trigger an RPM sense loss alarm. 

Natural gas grids can be impacted during major outage events or construction. Contact your natural gas supplier to verify any known issues in your area. 

Note: Most natural gas suppliers post outage or supply disruption alerts on their websites. 

Sometimes, checking user-serviceable components and performing recommended maintenance can temporarily or permanently resolve RPM sense loss issues. 

• Check the condition of the air filter. Blocked or restricted airflow can affect engine performance and lead to an RPM sense loss alarm.  
• Verify maintenance items have been completed per the maintenance schedule. 
• Where Can I Find the Maintenance Schedule for My Generac Home Standby Generator?

• Improper fuel pressure or dirty/poor quality fuel can contribute and/or prevent the unit from starting. However, due to the specialized equipment and safety considerations involved, fuel pressure and fuel quality checks must be performed by a professional. 
• Before considering fuel pressure or fuel quality, it's important to follow a systematic diagnostic process with a Generac IASD. Think of this like checking a low tire—before replacing it, you would first check the air pressure and see if it holds air. Similarly, fuel pressure or fuel quality issues should only be evaluated after ruling out other common causes outlined above.
• If all other troubleshooting checks do not resolve the issue, work with your dealer to determine whether contacting your gas supplier to verify fuel pressure or fuel quality is the next logical step in the troubleshooting process. 

If the RPM Sensor Loss error occurs during an outage, note the following: 

Battery considerations:

• The battery is charged through a direction connection to utility power. 
• If the battery was weak, or struggled to hold a charge prior to the outage, or has worn down due to an extended outage it may not hold enough charge which would cause issues on the restart. 
• Typically, there would have been an indication that there was an issue with the battery prior to the RPM Sensor Loss or in addition to the RPM Sensor Loss, though not always. 

Fuel system considerations:

During extended outages it is best practice to verify fuel levels and/or availability. 

• If your unit runs on Liquid Propane (LP), verify levels are about 30%.
• If you unit runs on Natural Gas (NG), consider potential grid stability issues during widespread outages, high demand, or natural disasters which can impact the grid systems. 

Note: Most natural gas suppliers post outage or supply disruption alerts on their websites. 

Most generators do not exercise under load; consider fuel and maintenance-related checks for those models. Next Generation Air-Cooled Standby generators do have the ability to exercise with a load transfer, but this option must be configured by the homeowner or installer. If you have a Next Generation model, verify if this option is enabled before proceeding through this section.

Questions to ask

• Check for repeated behavior.
• If your unit consistently triggers an RPM Sensor Loss alarm during exercise, note the conditions surrounding the unit's exercise time/ time of year. 
• Are you able to start the unit manually after receiving the fault?
• Repeatable errors should be inspected by a Generac IASD.
• If the error appears intermittently see the scenario section on intermittent errors.

If an RPM Sensor Loss alarm occurs during installation, the issue is most commonly related to the fuel system or an undercharged battery. One of the most frequent causes for issues during installation is an undercharged battery.

What to know about new batteries and charging requirements:

For new installations with new batteries, this error can commonly be caused by an undercharged battery. Even new batteries should complete a full 24-hour charge cycle before use, as they may lose charge due to shelf time, temperature fluctuations in storage or transportation, or through natural discharge. If the alarm appears when attempting to start the unit, allowing a full battery charge cycle should be the first troubleshooting step. 

Fuel system basic checks:

• Preform basic user resolvable fuel system checks outlined in the troubleshooting section above.  

Confirm fuel system compliance with installation requirements:

• The installer should coordinate with the gas provider to ensure the fuel system meets all specifications outlined in the installation manual. 
  • Where can I find an installation manual for my home standby generator?
• Ensure proper fuel system leaks test is preformed and fuel pressure is with in installation specification.

Note: Fuel pressure and fuel system leak tests should be preformed by a licensed professional.

Evaluate load-related factors (If issues occurs during load testing):

• If the RPM Sensor Loss alarm happens only when a load is applied, such as during a simulated power outage test, load management should be reviewed. 
• Work with your Generac IASD to determine if adjustments are needed for large appliances that may be activating simultaneously. 

Important warranty consideration:

• • Issues caused by improper installation are not covered under warranty. Ensuring proper fuel system setup by a qualified professional is essential for reliable operation. If an overspeed alarm occurs during installation, contact your installer immediately to verify installation requirements.

Diagnosing intermittent issues can be challenging because they are difficult to consistently replicate. However, owners can assist in the process by identifying patterns and noting key details when the issue occurs. This information helps Generac IASDs diagnose the root cause more efficiently. 

Identifying patterns to assist in diagnosis

Does the issue occur during an outage with a load applied?

• Pay attention to whether the RPM Sensor Loss alarm happens when a specific appliances such as a pool heater or large air conditioning unit, are activated. 
• If the issue occurs when these high-power devices turn on, the problem may be related to, overload, load management, or sudden electrical demand changes. 

Does the issue occur during exercise mode?

• If the unit experiences overspeed alarms while running without any load applied, focus on fuel system factors. 

Seasonal Weather and environmental factors

• In some geographic areas, seasonal changes can surface issues what were previously unnoticed.
• Extreme cold in areas that don't normally experience it can affect external systems that supply fuel to the unit, such as an external regulator not rated for rare extreme cold for your area. 
• Slight fuel pressure deviations that do not cause problems in warmer months may result in noticeable issues during the coldest winter months - this is more common in newly installed units which did not meet all installation requirements and specifications. 
• If the issue coincides with seasonal shifts, it's important to discuss these conditions with your Generac IASD to determine if adjustments are needed. 

Have there been any changes to your fuel system?

• Significant changes in fuel demand, such as adding large gas appliances may impact your system.

Note: This information is intended only to help owners provide useful context to a Generac IASD technician when diagnosing difficult-to-replicate errors. It is not a self-diagnosis guide. Diagnosing and resolving intermittent overspeed alarms required specialized tools and expertise, and a Generac IASD should always be consulted for proper evaluation. 

For additional information on troubleshooting intermittent alarms see the follow article:

• Troubleshooting intermittent or difficult to replicate alarms, faults, and error codes

• Inspect Battery: During cold weather, batteries perform worse because low temperatures slow chemical reactions, increase resistance, and reduce power output. Checking the battery's health in extreme cold is generally the first thing to check: How Do I Inspect the Battery On My Home Standby Generator?
• Inspect Air filter: During cold weather, moisture can freeze in the air filter, preventing adequate airflow to the engine: How Do I Check and Change the Air Filter On My Home Standby Generator?
• Snow buildup can also block airflow around the filter and cause this warning. Snow must be cleared from around the unit: Clearing the surrounding area of debris and snow for Home Stand by Generators
• See the What do I do when I expect a snow storm, or if there is snow building up around the unit? article for more information.

• When issues occur within the first year, it may suggest that aspects related to the installation should be considered as potential factors. Certain components may not show problems immediately, but issues can surface when specific circumstances arise due to seasonal changes and weather conditions. 

• When issues occur after the first year, it may suggest that aspects related to routine maintenance should be considered as potential factors.  Over time, regular wear and changes in usage conditions can make proper maintenance essential to prevent problems