Reznor 3 Flashes Error Code

What does Reznor 3 Flashes mean?

Three flashes of the UT controller diagnostic LED mean the control has gone into lockout after three unsuccessful ignition trials. The burner attempted to light but flame was not established on any of the allowed trials, so the controller shuts off the gas and locks out to prevent unburned gas from accumulating. The heater stays off until the lockout is reset.

Symptoms

• Diagnostic LED flashes three times, repeatedly
• Heater attempts to light then stops with no flame
• Burner is locked out and produces no heat
• Repeated ignition attempts heard before lockout

Common causes

• No gas, low gas pressure, or a closed manual gas valve
• Failed or misadjusted spark/ignition electrode or spark lead
• Dirty, misaligned, or faulty flame sensor
• Faulty gas valve not opening on demand
• Burner controller fault

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Diagnostic steps

1. Confirm the flash count

   Verify the controller LED is showing three repeating flashes to confirm an ignition-trial lockout rather than a pressure or hardware fault.

2. Verify gas supply

   Confirm the manual gas valve is open and the heater is receiving gas at the correct supply pressure.

3. Inspect ignition components

   Check the spark electrode, spark lead, and flame sensing components for damage, fouling, or poor positioning that would prevent flame from being proven.

4. Reset and observe

   Clear the lockout per the operating instructions and watch one full ignition sequence; if it locks out again, the gas valve or burner controller may need service or replacement.

When to call a professional

An ignition-trial lockout points to a gas delivery, ignition, or flame-proving problem, all of which involve live gas. The manual requires shutting off gas and electrical supplies before replacing the burner controller, gas valve, or related parts. If the heater locks out again after a reset and a gas-supply check, have a qualified gas heating technician diagnose the ignition system and gas valve rather than repeatedly resetting the control.