What Do the Green, Yellow, Blue and Red Status Indicator Lights Mean on Home Standby Generators?

This article explains what the green, yellow, red, and blue LED lights mean on Generac Next Generation and Guardian Series air-cooled standby generators. It clarifies the difference between maintenance reminders, non-critical warnings, and alarm codes, helping customers understand why a yellow maintenance light or red fault light may appear. Customers searching for “yellow maintenance light,” “generator service indicator,” “clear maintenance reminder,” “standby generator warning light,” or “LED status meaning” will find step-by-step guidance to identify alerts and confirm the generator is ready for reliable automatic operation.

  • May 28, 2026
  • Knowledge

Title
What Do the Green, Yellow, Blue and Red Status Indicator Lights Mean on Home Standby Generators?
URL Name
What-Do-the-Green-Yellow-and-Red-Status-Indicator-Lights-Mean-on-Home-Standby-Generators

Public Answer

Home standby generator LEDs

Generac standby generators use LED lights to indicate operating status. The lights, visible through a translucent lens on the side of the generator, change color or flash to show whether the unit is ready, running under load, needs routine maintenance, or requires service. 

Related resources

Environment

This article applies to Generac air-cooled home standby generators and liquid-cooled home standby generators equipped with an Evolution controller.

Indicator lens example 1

For Next Generation Series generators, see here.

Indicator lens example 2

For Guardian Series generators (2017–present), see here.

For liquid-cooled generators with an Evolution controller, see here.

Guardian series generator LEDs

Guardian LED lens callouts

  • Green (A): “Ready” status. Illuminates when utility power is present and the unit is in AUTO. Flashes during an outage when the unit is running.
  • Red (B): “Alarm” status. Illuminates when the generator is OFF or a shutdown alarm is detected. Most alarm codes require an authorized service dealer. See the How Can I Find a Generac Service Dealer in My Area? article.
Note: For more information on resetting a red light, see: How Do I Clear an Error or Alarm Code On My Home Standby Generator?
  • Yellow (C): “Non-critical alert” status. Illuminates when maintenance is due or a warning is present.
Note: For more information on resetting the maintenance reminder, see: How do I clear a yellow maintenance reminder or warning on my standby generator?

LED combinations

Multiple LEDs can be illuminated at the same time.

  • A red light can occur in combination with either a green or yellow light.
  • A yellow maintenance light can occur in combination with either a red or green light. For more information on resetting the maintenance reminder, see: How do I clear a yellow maintenance reminder or warning?
Note: Certain combinations (like red and yellow together) can be confused with an orange status.

Troubleshooting

Check the control panel. The LED lights work in tandem with the control panel to indicate what needs attention.

Liquid-cooled generators with an Evolution controller

On some liquid-cooled generators featuring an Evolution controller, it is possible to see both the red OFF LED and the green AUTO LED illuminated at the same time. These LEDs may be visible from the exterior of the unit through the controller’s viewing window.

  • Green AUTO LED illuminated with a solid red OFF LED: The generator is in AUTO mode and a warning message is present (for example, Charger Missing AC, Inspect Battery, or similar). Check the controller display for the warning details and address the condition.
  • Blinking red OFF LED: A fault is present (for example, Overcrank, Overspeed, or similar). Check the controller display for the alarm code and follow the recommended service steps. Dealer service may be required.

Next Generation series generator LEDs

Four LEDs are visible behind a translucent lens on the generator side panel. These LEDs indicate generator operating status.

Note: For detailed information on the meaning of an LED indicator, and to check the generator's current status, reference the Mobile Link app or the Mobile Link website.

Next Generation LED lens callouts

Green

  • The Green LED “Ready” light (A) illuminates when utility is present and the control panel is in AUTO. It flashes in one-second intervals when the automatic transfer switch converts to generator power during a utility outage, and in two-second intervals if utility power is lost and the unit is in the delay timer period before cranking/starting.

Yellow

  • The Yellow LED “MANUAL” or “Non-critical alert” light (C) illuminates when the control panel is in MANUAL and the unit is running. It flashes in one-second intervals when a warning is active or maintenance is required. If flashing, the generator should still run during an outage, but the alert should be addressed promptly. To see which alert is active, reference the Mobile Link app or the Mobile Link website. The Yellow LED may be illuminated at the same time as either the Red or Green LED.
Note: For more information on resetting the maintenance reminder, see: How do I clear a yellow maintenance reminder or warning on my standby generator?

Red

  • The Red LED “Alarm” light (B) illuminates when the generator is OFF. It flashes in one-second intervals when a fault is detected. If the Red LED is illuminated, service from a Generac dealer may be required: What Error Codes Do I Need to Call a Dealer For?
Note: For more information on resetting a red light, see: How Do I Clear an Error or Alarm Code On My Home Standby Generator?

Blue

  • The Blue LED “Service Mode” light (D) illuminates when the control panel is in SERVICE mode. The Blue LED may be illuminated at the same time as any other LED.
Note: For more information on resetting a blue light, see: How do I turn off service mode?

Troubleshooting

Owners should reference the Mobile Link app or the Mobile Link website for detailed LED meanings and current generator status. The LEDs work in tandem with the control panel and Mobile Link to indicate what needs attention.

Maintenance

If it is determined that a generator requires maintenance, the owner can contact an authorized service dealer using the dealer locator or perform maintenance if comfortable doing so: Where Can I Find the Maintenance Schedule for My Generac Home Standby Generator?

The maintenance schedule is listed in the generator owner's manual: How Do I Find a Copy of My Home Standby Generator Owner's Manual, Spec Sheets, or Installation Manual?

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