Weil-McLain Water Heaters Error Codes

Blocked Vent

Control displays 'Blocked Vent', 'Vent Block', or similar; inducer may run but burner will not fire.

Vent System Obstruction

Circulator Fault

Control indicates 'Circulator Fault', 'Pump Error', or similar; water heater may overheat or fail to deliver hot water.

Circulator Pump Failure or Control Issue

Condensate Blocked

Control indicates 'Condensate Blocked' or 'Drain Fault'; unit may shut down and display a fault.

Condensate Drain Obstruction

Flame Detected with No Call

Control indicates 'Flame Present' or 'Flame Detected' when there is no call for heat; unit may lock out.

False Flame Sensing

Flame Failure

Burner lights briefly then shuts off; control displays 'Flame Failure' or similar and may retry several times.

Loss of Flame Signal During Operation

Flue Temperature High

Control displays 'Flue Temp High' or similar; burner shuts down and may lock out until reset.

Excessive Flue Gas Temperature

Hard Lockout

Water heater will not fire; control display or LED indicates 'Hard Lockout' and burner remains off until power is cycled or reset button is pressed.

Primary Safety Lockout Condition

High Limit Open

Control indicates 'High Limit Open' or 'High Temperature Limit'; burner will not fire until the limit resets.

High Temperature Safety Trip

Ignition Failure

Control indicates 'Ignition Failure' or similar; burner does not light and unit retries several times before locking out.

Failed Burner Ignition Sequence

Inlet Temperature Sensor Fault

Control indicates 'Inlet Sensor Error', 'Return Sensor Fault', or similar; water temperature control may be unstable.

NTC Temperature Sensor Failure (Inlet)

Internal Control Fault

Control displays 'Internal Error', 'Control Fault', or random/unstable codes; unit may behave unpredictably.

Electronic Control Board Failure

Low Gas Pressure

Control displays 'Low Gas Pressure' or similar; burner may light weakly or not at all, then lock out.

Insufficient Gas Supply to Burner

Low Water Cutoff

Control indicates 'Low Water' or 'LWCO'; burner is disabled and may show a lockout or alarm condition.

Low Water Cutoff Safety Activation

Outlet Temperature Sensor Fault

Control indicates 'Outlet Sensor Error', 'Supply Sensor Fault', or similar; unit may shut down or operate erratically.

NTC Temperature Sensor Failure (Outlet)

Pressure Switch Open

Control indicates 'Pressure Switch Open' or similar; inducer may run but burner will not light.

Combustion Air/Exhaust Pressure Switch Not Proving

Pressure Switch Stuck Closed

Control indicates 'Pressure Switch Closed' when idle; unit will not start a new cycle.

Combustion Pressure Switch Not Opening at Rest

Rollout Switch Open

Control indicates 'Rollout Switch Open' or 'Flame Rollout'; burner is disabled until manual reset.

Flame Rollout Safety Trip

Sensor Open

Control shows 'Sensor Open' or similar; temperature reading may show extremely low or negative value.

Open-Circuit NTC Sensor

Sensor Shorted

Control shows 'Sensor Short' or similar for a specific temperature sensor; reading may show extremely high temperature.

Short-Circuited NTC Sensor

Soft Lockout

Water heater intermittently shuts down with 'Soft Lockout' indicated; unit may restart automatically after a delay or after a manual reset.

Temporary Safety Lockout Condition

Tank Temperature Sensor Fault

Indirect-fired Weil-McLain water heater does not maintain set temperature; boiler control shows 'Tank Sensor Error' or similar.

Domestic Hot Water Tank Sensor Failure

Symptom

Condensation or water appears on the outside of the Weil-McLain water heater tank or piping.

External Condensation

Symptom

No hot water at faucets; Weil-McLain indirect water heater tank is cold even though boiler is operating normally.

No Domestic Hot Water Production (Indirect Tank)

Symptom

Temperature and pressure relief (T&P) valve on the Weil-McLain water heater drips or discharges water periodically.

Relief Valve Discharge

Symptom

Water is too hot at faucets; temperature fluctuates and may exceed safe levels.

Overheating Domestic Hot Water

Symptom

Water is warm but not hot enough; Weil-McLain water heater cannot reach set temperature or recovery is very slow.

Insufficient Hot Water Temperature

Symptom

Weil-McLain indirect water heater causes boiler to run constantly, even when no hot water is being used.

Continuous DHW Call

Symptom

Weil-McLain indirect water heater provides hot water initially, then quickly runs cold during use.

Rapid Hot Water Depletion

Symptom

Weil-McLain water heater burner is very noisy, with roaring or whistling sounds during operation.

Abnormal Combustion Noise

Symptom

Weil-McLain water heater cycles on and off frequently with short run times, even with steady hot water demand.

Short Cycling

Symptom

Weil-McLain water heater makes rumbling, popping, or kettling noises during heating.

Boiling and Scale Buildup in Heat Exchanger or Tank

Symptom

Weil-McLain water heater or indirect tank emits a sulfur or rotten egg odor from hot water taps.

Hydrogen Sulfide Odor in Hot Water

Symptom

Weil-McLain water heater or indirect tank is leaking water onto the floor.

Tank or Piping Water Leak

Symptom

Weil-McLain water heater trips the electrical breaker or blows fuses when it attempts to start.

Electrical Overload or Short Circuit

Symptom

Weil-McLain water heater will not start at all; no lights or display on the control.

No Power to Water Heater

Symptom

Weil-McLain water heater’s burner starts but shuts down after a few seconds without showing a specific code; LED may blink briefly.

Unstable Flame or Safety Trip Without Display Code

Symptom

Weil-McLain water heater’s combustion air intake is drawing in lint, dust, or debris from the mechanical room.

Contaminated Combustion Air

Symptom

Weil-McLain water heater’s vent pipe shows signs of corrosion, white residue, or water dripping from joints.

Condensate and Vent Corrosion Issues