What Does It Mean When My Generator Displays an alarm: Undervoltage, error codes 1900-1916?

A sudden drop in the generator's output voltage can trigger this error code.  For this code, please contact an authorized service dealer for assistance.

  • Aug 26, 2025
  • Knowledge

Title
What Does It Mean When My Generator Displays an alarm: Undervoltage, error codes 1900-1916?
URL Name
What-Does-It-Mean-When-My-Generator-Displays-an-Error-Code-Undervoltage-Code-1900

Public Answer

Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns. 

 

Undervoltage: Error Codes 1900-1916

 

Environment

This article applies to:
  • Generac Next Generation Series 10-28 kW air-cooled standby generators
  • Generac Guardian Series 10-26 kW air-cooled standby generators (2017 to present)

Note: The term "error code" is used interchangeably with 'alarm code,' 'fault code,' 'fault alarm' and similar terminology. Error code applies to all such terminology. 

Overview

  • Error codes: 1900-1906
  • LED Indicator: Red
  • Fault: UNDERVOLTAGE
  • Issue: The generator is not producing proper voltage. This could result from prolonged under voltage or sudden voltage loss.
  • Cause: Often linked to fuel supply/selection issues, circuitry, firmware, or voltage production. While basic checks, like verifying fuel supply/selection and restarting can be attempted, the electrical nature of this issue typically requires advanced diagnosis by a Generac Independent Authorized Service Dealer (IASD)

What can I do?

  • Your options are limited beyond performing basic troubleshooting checks on components and verifying that everything appears normal.
  • You can attempt to clear the alarm and manually restart the unit: How Do I Clear an Error or Alarm Code On My Home Standby Generator?
  • Sometimes, clearing the alarm and attempting to restart the unit is all that is needed, as the alarm may be a one-time occurrence that does not indicate a persistent issue.

Note: Never start a generator while under load. See the scenario-based considerations below for troubleshooting in an outage/utility power failure.

When should you contact a Generac Independent Authorized Service Dealer (IASD)?

  • If issues persist after performing the checks and attempting to restart, contacting a Generac IASD for diagnosis is strongly recommended. 

 

General troubleshooting steps

Fuel supply or fuel selection:

The undervoltage error code can occur due to fuel selection or supply issues. Air-cooled home standby generators are designed to operate on either Liquid Propane (LP) or Natural Gas (NG) and can be converted in the field.

Note: The below steps only apply to Guardian series generators. For Next Generation series generators, fuel conversion takes place in the Field Pro app during initial installation: How Do I Perform a Fuel Conversion on My Air-Cooled Home Standby Generator?

Fuel conversion requires correct fuel jet positioning and proper fuel type selection in the controller. If the jet position and fuel type settings in the controller do not align with the actual fuel source, it can disrupt operation, affect voltage output, and potentially trigger an undervoltage alarm.

Note: In extreme weather event circumstances, heavy load on the fuel supply grid may result in a decrease in available fuel to the unit, which may result in an error 1902.

Troubleshooting actions

1. Perform checks above.

 

2. Clear the alarm at the generator's control panel: How Do I Clear an Error or Alarm Code On My Home Standby Generator?

 

3. Attempt to start the unit manually by pressing the blue MANUAL button on the controller. 

 

Note: Never start a generator while under load. See the scenario-based considerations below for troubleshooting in an outage/utility power failure.

Scenario-based considerations

 

A. In an outage/utility power failure
B. During installation
D. Extreme Cold/Winter Conditions
E. Units installed within the last year
  • 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. 
F. Units installed for longer than a year
  • 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. 

Next Steps: When troubleshooting works or fails

Troubleshooting worked
  • If troubleshooting was successful, take note of the potential factors that may have contributed to the fault alarm. 
  • Considerations such as weather, season, loads, and other situational factors surrounding the occurrence may help identify external factors if the issues arise again.
Troubleshooting failed
  • If the unit fails to start and run after performing the outlined troubleshooting steps, contact a Generac IASD. 
  • Diagnosing the causes of engine speed issues can be complex and requires accessing components that could harm the owner or generator. Generac recommends contacting an authorized service dealer for assistance.
Working with a Generac IASD for diagnosis and repair
  • Only a Generac IASD can submit warranty claims and perform warranty repairs.
  • Leave the error code present on the unit so it can be properly diagnosed.
  • Keep records of all maintenance performed.
  • Note any situational factors or details related to the alarm occurrence; this information may help the technician diagnose the issue more effectively. 
  • How Can I Find a Generac Service Dealer in My Area?

Additional resources

 



 
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