Reznor 5 Flashes Error Code

What does Reznor 5 Flashes mean?

Five flashes of the UT controller diagnostic LED indicate the burner controller has detected an internal hardware fault. The control's self-check has found a problem within its own electronics rather than an external switch, gas, or flame condition. Because the safety control cannot be trusted to operate reliably, the heater will not fire until the fault is resolved.

Symptoms

• Diagnostic LED flashes five times, repeatedly
• Heater will not start despite a call for heat
• Fault persists regardless of gas and airflow checks
• No response to normal reset attempts

Common causes

• Internal failure of the burner controller electronics
• Power supply problem affecting the controller
• Damaged controller from moisture, heat, or electrical stress
• Faulty wiring harness connection to the controller

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Diagnostic steps

1. Confirm the flash count

   Verify the controller LED is showing five repeating flashes, which the manual identifies as a control hardware fault.

2. Check power and connections

   Confirm the heater has correct, stable supply power and that the controller wiring harness connector is fully seated.

3. Cycle power

   Remove and restore power to the heater to see whether the hardware fault clears, indicating a transient versus a hard failure.

4. Replace the burner controller

   If the fault persists, follow the IOM burner controller replacement procedure after shutting off gas and all electrical supplies.

When to call a professional

A control hardware fault means the safety control itself has failed self-check, and the heater should not be forced to run. Replacing the burner controller involves working inside the gas-fired chassis with the gas and electrical supplies shut off as the manual requires. Have a qualified gas heating technician confirm the fault and install a correct replacement controller; do not bypass or jumper the control to force operation.