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Error code reference

Bradford White Water Heater Error Code 23

Flame detected before ignition.

Bradford White codesBradford White water heater codes

Flame detected before ignition.

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What 23 means on a Bradford White water heater

Error code 23 on a Bradford White water heater indicates that the control board has detected a flame signal in the burner assembly before the ignition sequence has been initiated. Under normal operation, the control board sends a call for ignition, opens the gas valve, and activates the igniter before any flame signal should be present. When the flame sensor reports current flowing through it prior to this sequence starting, the control interprets this as an unsafe condition and locks out the system to prevent uncontrolled combustion.

The most likely technical cause is a faulty or contaminated flame sensor that is generating a false signal. The flame sensor works by passing a small DC microamp current through the flame, using the principle of flame rectification. If the sensor rod is coated with residue, cracked, or shorted to ground, it can produce a spurious signal that the control board reads as an active flame. A failed gas valve that is leaking gas and allowing combustion to continue between cycles is another serious possibility, as residual gas could ignite and trigger the sensor before the control board expects it.

Additionally, a faulty control board with a defective flame sensing circuit may misinterpret input signals and log error code 23 even when the sensor and gas valve are functioning correctly. Wiring issues such as a short in the flame sensor lead or moisture intrusion into the connector can also cause false flame detection readings. Each of these conditions requires careful diagnosis before parts are replaced.

Source: manufacturer service documentation.

Common causes of 23

  1. 01

    Faulty or contaminated flame sensor

    Part replacement

    A flame sensor rod coated with oxidation, carbon deposits, or other residue can produce a false signal even when no flame is present. Inspect the sensor rod for buildup or visible damage and test microamp output if possible.

  2. 02

    Gas valve leaking or not closing fully

    Part replacement

    A gas valve that fails to fully close between heating cycles can allow gas to seep into the combustion chamber, resulting in unintended ignition. This is a serious safety concern and the valve should be inspected or replaced by a qualified technician.

  3. 03

    Short or wiring fault in the flame sensor circuit

    Wiring / connection

    A pinched, damaged, or moisture-affected wire in the flame sensor lead can create a short that mimics a flame detection signal. Inspect the wiring harness from the sensor to the control board for visible damage or corrosion at connectors.

  4. 04

    Failed control board

    Part replacement

    A defective control board with a malfunctioning flame sense input circuit may falsely register a flame signal before ignition even when all other components are operating correctly. This is typically a diagnosis of exclusion after other causes are ruled out.

  5. 05

    Residual flame from previous cycle

    Part replacement

    In some cases, a lingering flame from a previous heating cycle that did not extinguish properly can be detected by the sensor at the start of the next call for heat. This may point to a problem with gas valve shutoff or burner orifice blockage.

See the test procedure for each cause

Frequently asked questions about 23

What does 23 mean on a Bradford White water_heater?
Error code 23 means the control board detected a flame signal before the ignition sequence was initiated. This is a safety lockout condition indicating the system sensed combustion at a time when the burner should not be active. The water heater will shut down and refuse to operate until the cause is diagnosed and resolved.
Can I reset the water heater to clear error code 23?
You may be able to clear the lockout temporarily by resetting the unit, but if the underlying cause is not corrected, error code 23 will return. A reset does not fix a faulty flame sensor, a leaking gas valve, or a wiring short. Resetting repeatedly without diagnosing the root cause is not recommended and could mask a potentially unsafe condition.
Is error code 23 on a Bradford White water heater a safety concern?
Yes, this error code should be taken seriously. A flame detected before ignition can indicate a gas valve that is not closing properly or other combustion control issues. Do not attempt to bypass the lockout. If you suspect a gas leak or smell gas near the unit, shut off the gas supply and contact a qualified technician or your gas utility immediately.
How do I fix error code 23 on my Bradford White water heater?
Start by inspecting the flame sensor rod for contamination, damage, or a shorted wire in the sensor lead. If the sensor appears clean and the wiring is intact, the gas valve should be evaluated to confirm it closes fully between cycles. If both components check out, the control board may need to be tested or replaced. Given the safety implications of this error, many homeowners choose to have a licensed plumber or HVAC technician perform this diagnosis.
How much does it cost to repair error code 23 on a Bradford White water heater?
Repair costs depend on the faulty component. A flame sensor replacement is typically the least expensive fix, with parts and labor ranging from around $75 to $200. A gas valve replacement is more involved and can range from $200 to $500 or more depending on labor rates and the specific model. Control board replacement falls in a similar range. A diagnostic service call alone may cost $75 to $150 before any parts are factored in.

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