Reznor 4 Flashes Error Code

What does Reznor 4 Flashes mean?

Four flashes of the UT controller diagnostic LED mean the control has locked out after losing the flame signal five times. The burner lit successfully but the flame was not sustained, dropping out repeatedly during the heat cycle. After the fifth flame loss the controller locks out and shuts off gas to prevent unsafe operation, keeping the heater off until it is reset.

Symptoms

• Diagnostic LED flashes four times, repeatedly
• Burner lights but flame goes out shortly after
• Heater short-cycles before locking out
• No sustained heat output

Common causes

• Weak flame signal from a dirty or worn flame sensor
• Unstable or low gas pressure causing flame dropout
• Poor burner combustion or partial blockage affecting flame
• Marginal combustion airflow disturbing the flame
• Faulty gas valve or burner controller

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Diagnostic steps

1. Confirm the flash count

   Verify the controller LED is showing four repeating flashes to confirm a flame-loss lockout.

2. Check the flame sensor

   Inspect the flame sensing electrode for fouling, corrosion, or misalignment that would weaken the flame signal during the heat cycle.

3. Verify gas pressure stability

   Confirm the gas supply pressure is steady and within specification, since drops can cause the flame to drop out repeatedly.

4. Reset and monitor a full cycle

   Clear the lockout and watch a complete heat cycle; if flame loss recurs, the gas valve or controller may need professional service per the IOM parts-replacement procedures.

When to call a professional

Repeated flame loss involves combustion stability and gas pressure issues that need instrumentation and gas-safety knowledge to diagnose correctly. The manual requires turning off gas and electrical supplies before replacing the gas valve or burner controller. If the LED still shows four flashes after cleaning the flame sensor and confirming gas pressure, have a qualified gas heating technician evaluate combustion, gas pressure, and the control before returning the heater to service.