Generator continues to run after utility power has been restored; transfer switch may or may not retransfer.

Safety first: Verify utility power is stable and within normal voltage before forcing any transfer. Use proper PPE when working in live panels.

• Check utility voltage: Measure voltage at the ATS utility terminals to confirm power is present and within spec.
• Inspect sensing wiring: Ensure the utility sensing leads to the Guardian controller are intact and properly connected.
• Controller settings: Verify retransfer delay and sensing thresholds in the controller menu.
• Manual retransfer: If safe and per Guardian instructions, manually retransfer the ATS to utility and place the generator in OFF.
• Service boards: If the problem recurs, the ATS or generator control board may need replacement.