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Error code reference

Bradford White Water Heater Error Code 34

Combustion air temperature sensor is faulty.

Bradford White codesBradford White water heater codes

Combustion air temperature sensor is faulty.

First step from the service manual

Check sensor wiring for damage. Check resistance on sensor. Check and clean dirt from sensor. Ensure fan blade is tight on motor shaft and is in good condition. Clean blower blades if dirty. Check for restrictions in air flow around unit and vent terminal. Replace sensor.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 34 means on a Bradford White water heater

Error code 34 on a Bradford White water heater indicates a fault with the combustion air temperature sensor. This sensor monitors the temperature of the air entering the combustion chamber and is a critical component of the unit's safety and efficiency controls. When the control board detects a reading from this sensor that falls outside the expected range, either due to an open circuit, a short, or an out-of-range resistance value, it triggers error code 34 and shuts down the burner to prevent unsafe operation.

The combustion air temperature sensor works in conjunction with the blower assembly, which draws air into the combustion chamber for the burner. Because the sensor is located in the airstream, its readings are directly affected by actual airflow conditions. A dirty or obstructed blower, a loose or damaged fan blade, or restricted airflow around the unit or at the vent terminal can cause abnormal temperature readings at the sensor even if the sensor itself is functioning correctly. These airflow-related issues must be ruled out before concluding the sensor has failed.

Common root causes include damaged or corroded sensor wiring, sensor contamination from dust or debris, and physical sensor failure. The diagnostic process involves inspecting the wiring harness for damage, measuring the sensor's resistance to verify it matches expected values, cleaning any dirt from the sensor body, and inspecting the blower assembly for loose fan blades or fouled blades. Restrictions in the air intake path or vent terminal should also be cleared. If all other checks pass, replacing the sensor is the final step.

Source: manufacturer service documentation.

Common causes of 34

  1. 01

    Sensor contamination or dirt buildup

    Wiring / connection

    Dust and debris can accumulate on the combustion air temperature sensor over time, causing it to read inaccurately. Inspect the sensor visually and clean it carefully before assuming sensor failure.

  2. 02

    Damaged or corroded sensor wiring

    Wiring / connection

    The wiring harness connecting the sensor to the control board may have broken, frayed, or corroded connections that disrupt the signal. Inspect all wiring from the sensor back to the board for visible damage or loose connectors.

  3. 03

    Restricted airflow at unit or vent terminal

    Wiring / connection

    Obstructions around the water heater or at the vent terminal can reduce airflow enough to cause abnormal sensor readings. Clear any debris, lint, or obstructions from both the air intake area and the vent exhaust terminal.

  4. 04

    Loose or damaged fan blade on blower motor

    Part replacement

    A fan blade that is loose on the motor shaft or physically damaged will reduce airflow through the blower assembly and affect sensor readings. Check that the blade is firmly secured to the shaft and inspect for cracks or missing sections.

  5. 05

    Failed combustion air temperature sensor

    Part replacement

    If wiring, airflow, blower condition, and cleanliness have all been confirmed acceptable, the sensor itself may have failed and is producing an out-of-range resistance value. Measure the sensor resistance and replace the sensor if the reading does not match expected specifications.

See the test procedure for each cause

Frequently asked questions about 34

What does 34 mean on a Bradford White water_heater?
Error code 34 means the control board has detected a fault with the combustion air temperature sensor. This sensor monitors the temperature of air entering the burner assembly, and the code is triggered when the sensor signal falls outside the acceptable range. The heater shuts down the burner as a safety response until the issue is diagnosed and corrected.
Can I fix error code 34 myself on a Bradford White water heater?
Some of the steps involved are DIY-friendly, such as checking for airflow restrictions around the unit and vent terminal, cleaning debris from the sensor, and inspecting visible wiring for damage. However, measuring sensor resistance and replacing internal components requires basic electrical knowledge and comfort working around gas appliances. If you are unsure about any step, contacting a qualified technician is the safer choice.
Is it safe to use my water heater while error code 34 is active?
No. When error code 34 is active, the Bradford White control board has shut down the burner as a precautionary measure. The unit will not heat water normally in this state, and attempting to bypass the shutdown is not recommended. The combustion air temperature sensor is part of the safety system, and the heater should remain out of service until the fault is resolved.
Will resetting the water heater clear error code 34?
A reset may temporarily clear the error display, but if the underlying problem with the sensor, its wiring, or the airflow system has not been addressed, the code will return. Resetting without diagnosing the cause is not a fix. Work through the full diagnostic process, including sensor cleaning, wiring inspection, blower condition check, and airflow verification, before relying on a reset.
How much does it cost to repair error code 34 on a Bradford White water heater?
Repair costs vary depending on the root cause. If the fix involves only cleaning the sensor or clearing an airflow restriction, costs may be minimal. If the combustion air temperature sensor needs replacement, parts typically range from around $30 to $80 depending on the model, with labor adding to the total if a technician is involved. Blower assembly components, if the fan blade or motor is damaged, will increase the repair cost further.

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