Step1: Disconnect power and gas supply, and allow unit to cool completely before servicing.
Step2: Remove access panel and locate the existing thermocouple near the pilot or burner assembly.
Step3: Disconnect old thermocouple from the gas control valve and mounting bracket carefully.
Step4: Install new HD thermocouple, positioning tip securely in the flame zone.
Step5: Reconnect lead to control valve, ensuring tight and secure electrical connection.
Step6: Reassemble unit, restore gas and power, then test pilot flame and verify millivolt output for safe operation.