Weil-McLain
Weil-McLain Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
Advertisements
Blocked Intake
The boiler displays 'Blocked Intake', 'Air Block', or similar; it may fail to ignite or run erratically.
Combustion Air Intake Obstruction
Blocked Vent
The boiler shuts down and displays 'Blocked Vent', 'Vent Block', or similar; this may be accompanied by pressure switch faults.
Exhaust Vent Obstruction
Circulator Fault
Boiler indicates 'Pump Fault', 'Circulator Error', or similar; may overheat or short cycle.
Primary Circulator Pump Failure
Condensate Blocked
Condensing boiler shuts down with 'Condensate Block', 'Drain Fault', or similar; water may be visible in the base.
Condensate Drain Obstruction
Domestic Hot Water Sensor Fault
Boiler with indirect tank or combi function shows 'DHW Sensor Fault', 'Tank Sensor Open/Short', or DHW temperature is incorrect.
DHW Temperature Sensor Circuit Failure
Flame Detected with No Call
The control indicates 'Flame Detected' or similar, even though there is no call for heat and the burner is off.
False Flame Detection
Flame Failure
Boiler lights briefly, then shuts down. The display shows 'Flame Failure', 'Flame Loss', or similar, often followed by retries.
Loss of Flame Signal During Operation
Flue Temperature High
The boiler shuts down with 'Flue Temp High', 'Stack Temp', or similar; it may reset after cooling.
Excessive Flue Gas Temperature
Hard Lockout
The boiler will not fire; the control display indicates 'Hard Lockout' and may show an associated fault code, requiring a manual reset.
Primary Safety Lockout Condition
High Limit
The boiler shuts down and displays 'High Limit', 'HL', or 'Temperature Limit Exceeded'; it may reset after the water cools.
High Temperature Limit Trip
Ignition Failure
The boiler attempts to start; you may hear the fan and clicking, but the burner does not light, and the control shows 'Ignition Failure' or a similar message.
Failed Ignition Sequence
Limit String Open
Boiler will not fire and indicates 'Limit Open', 'Safety String Open', or similar; multiple safeties are wired in series.
Open Safety Limit Circuit
Low Gas Pressure
The boiler locks out with 'Low Gas Pressure', 'Gas Supply', or a similar message; it may have intermittent ignition failures.
Insufficient Gas Supply Pressure
Low Water Cutoff
The boiler will not fire and indicates 'Low Water', 'LWCO', or a low water cutoff fault; the gauge may show low or zero pressure.
Low Water Condition Lockout
Outdoor Sensor Fault
Boiler display shows 'Outdoor Sensor Fault', 'OD Sensor Open/Short', or outdoor temperature reads extremely high/low.
Outdoor Temperature Sensor Circuit Failure
Pressure Switch Closed
The control indicates 'Pressure Switch Closed' or 'Stuck Closed' when there is no call for heat; the boiler may not start.
Stuck or Shorted Air Pressure Switch
Pressure Switch Open
The boiler will not ignite; the control shows 'Pressure Switch Open', 'Air Proving Switch Open', or similar; the inducer may run continuously.
Combustion Air Proving Failure
Return Sensor Fault
Boiler indicates 'Return Sensor Fault', 'Return Temp Open/Short', or return temperature is stuck at an extreme value.
Return Water Temperature Sensor Failure
Rollout Switch Open
Boiler shuts down and indicates 'Rollout', 'Flame Rollout Switch Open', or similar; manual reset required.
Flame Rollout Safety Trip
Sensor Communication Error
Boiler display shows 'Comm Error', 'Sensor Bus Error', or similar; multiple sensor readings may be lost.
Control-to-Sensor Communication Failure
Soft Lockout
The boiler stops firing and displays 'Soft Lockout' or 'Lockout – Retry' but may automatically reset after a timeout.
Temporary Ignition or Flame Supervision Lockout
Supply Sensor Fault
Boiler shows 'Supply Sensor Fault', 'Supply Temp Open/Short', or supply temperature reading is unrealistic.
Supply Water Temperature Sensor Failure
Symptom
Boiler cycles on and off rapidly when only domestic hot water is used (combi models)
DHW Short Cycling on Combi Boiler
Symptom
Boiler does not start at all; no lights or display.
No Power to Boiler
Symptom
Boiler emits unusual odors (burning, metallic, or exhaust smell) during operation.
Abnormal Combustion or Overheating Odor
Symptom
Boiler frequently loses pressure over days or weeks without visible leaks.
Slow Pressure Loss in Closed System
Symptom
Boiler leaking water from bottom of cabinet
Internal Water Leak
Symptom
Boiler lockout occurs only during very cold or very windy weather
Weather-Related Combustion or Venting Issues
Symptom
Boiler makes loud banging or knocking noises when starting or stopping.
Water Hammer or Kettling
Symptom
Boiler pressure rises excessively during the heating cycle, and the relief valve discharges water.
Over-Pressurization of Hydronic System
Symptom
Boiler runs continuously and overshoots the thermostat setting.
Boiler Fails to Shut Off on Temperature
Symptom
Boiler runs, but radiators or baseboards stay cold.
No Heat to Distribution System
Symptom
Boiler short cycles (turns on and off frequently) without maintaining a steady temperature.
Short Cycling Operation
Symptom
Boiler vibrates excessively or is unusually noisy during operation.
Mechanical Vibration or Fan Imbalance
Symptom
Domestic hot water temperature fluctuates or runs out quickly on combi or indirect systems
Inconsistent Domestic Hot Water Production
Symptom
Radiators heat unevenly; some are hot while others remain cool.
Uneven Heat Distribution
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| Blocked Intake |
The boiler displays 'Blocked Intake', 'Air Block', or similar; it may fail to ignite or run erratically.
|
Combustion Air Intake Obstruction | View Details |
| Blocked Vent |
The boiler shuts down and displays 'Blocked Vent', 'Vent Block', or similar; this may be accompanied by pressure switch faults.
|
Exhaust Vent Obstruction | View Details |
| Circulator Fault |
Boiler indicates 'Pump Fault', 'Circulator Error', or similar; may overheat or short cycle.
|
Primary Circulator Pump Failure | View Details |
| Condensate Blocked |
Condensing boiler shuts down with 'Condensate Block', 'Drain Fault', or similar; water may be visible in the base.
|
Condensate Drain Obstruction | View Details |
| Domestic Hot Water Sensor Fault |
Boiler with indirect tank or combi function shows 'DHW Sensor Fault', 'Tank Sensor Open/Short', or DHW temperature is incorrect.
|
DHW Temperature Sensor Circuit Failure | View Details |
| Flame Detected with No Call |
The control indicates 'Flame Detected' or similar, even though there is no call for heat and the burner is off.
|
False Flame Detection | View Details |
| Flame Failure |
Boiler lights briefly, then shuts down. The display shows 'Flame Failure', 'Flame Loss', or similar, often followed by retries.
|
Loss of Flame Signal During Operation | View Details |
| Flue Temperature High |
The boiler shuts down with 'Flue Temp High', 'Stack Temp', or similar; it may reset after cooling.
|
Excessive Flue Gas Temperature | View Details |
| Hard Lockout |
The boiler will not fire; the control display indicates 'Hard Lockout' and may show an associated fault code, requiring a manual reset.
|
Primary Safety Lockout Condition | View Details |
| High Limit |
The boiler shuts down and displays 'High Limit', 'HL', or 'Temperature Limit Exceeded'; it may reset after the water cools.
|
High Temperature Limit Trip | View Details |
| Ignition Failure |
The boiler attempts to start; you may hear the fan and clicking, but the burner does not light, and the control shows 'Ignition Failure' or a similar message.
|
Failed Ignition Sequence | View Details |
| Limit String Open |
Boiler will not fire and indicates 'Limit Open', 'Safety String Open', or similar; multiple safeties are wired in series.
|
Open Safety Limit Circuit | View Details |
| Low Gas Pressure |
The boiler locks out with 'Low Gas Pressure', 'Gas Supply', or a similar message; it may have intermittent ignition failures.
|
Insufficient Gas Supply Pressure | View Details |
| Low Water Cutoff |
The boiler will not fire and indicates 'Low Water', 'LWCO', or a low water cutoff fault; the gauge may show low or zero pressure.
|
Low Water Condition Lockout | View Details |
| Outdoor Sensor Fault |
Boiler display shows 'Outdoor Sensor Fault', 'OD Sensor Open/Short', or outdoor temperature reads extremely high/low.
|
Outdoor Temperature Sensor Circuit Failure | View Details |
| Pressure Switch Closed |
The control indicates 'Pressure Switch Closed' or 'Stuck Closed' when there is no call for heat; the boiler may not start.
|
Stuck or Shorted Air Pressure Switch | View Details |
| Pressure Switch Open |
The boiler will not ignite; the control shows 'Pressure Switch Open', 'Air Proving Switch Open', or similar; the inducer may run continuously.
|
Combustion Air Proving Failure | View Details |
| Return Sensor Fault |
Boiler indicates 'Return Sensor Fault', 'Return Temp Open/Short', or return temperature is stuck at an extreme value.
|
Return Water Temperature Sensor Failure | View Details |
| Rollout Switch Open |
Boiler shuts down and indicates 'Rollout', 'Flame Rollout Switch Open', or similar; manual reset required.
|
Flame Rollout Safety Trip | View Details |
| Sensor Communication Error |
Boiler display shows 'Comm Error', 'Sensor Bus Error', or similar; multiple sensor readings may be lost.
|
Control-to-Sensor Communication Failure | View Details |
| Soft Lockout |
The boiler stops firing and displays 'Soft Lockout' or 'Lockout – Retry' but may automatically reset after a timeout.
|
Temporary Ignition or Flame Supervision Lockout | View Details |
| Supply Sensor Fault |
Boiler shows 'Supply Sensor Fault', 'Supply Temp Open/Short', or supply temperature reading is unrealistic.
|
Supply Water Temperature Sensor Failure | View Details |
| – |
Boiler cycles on and off rapidly when only domestic hot water is used (combi models)
|
DHW Short Cycling on Combi Boiler | View Details |
| – |
Boiler does not start at all; no lights or display.
|
No Power to Boiler | View Details |
| – |
Boiler emits unusual odors (burning, metallic, or exhaust smell) during operation.
|
Abnormal Combustion or Overheating Odor | View Details |
| – |
Boiler frequently loses pressure over days or weeks without visible leaks.
|
Slow Pressure Loss in Closed System | View Details |
| – |
Boiler leaking water from bottom of cabinet
|
Internal Water Leak | View Details |
| – |
Boiler lockout occurs only during very cold or very windy weather
|
Weather-Related Combustion or Venting Issues | View Details |
| – |
Boiler makes loud banging or knocking noises when starting or stopping.
|
Water Hammer or Kettling | View Details |
| – |
Boiler pressure rises excessively during the heating cycle, and the relief valve discharges water.
|
Over-Pressurization of Hydronic System | View Details |
| – |
Boiler runs continuously and overshoots the thermostat setting.
|
Boiler Fails to Shut Off on Temperature | View Details |
| – |
Boiler runs, but radiators or baseboards stay cold.
|
No Heat to Distribution System | View Details |
| – |
Boiler short cycles (turns on and off frequently) without maintaining a steady temperature.
|
Short Cycling Operation | View Details |
| – |
Boiler vibrates excessively or is unusually noisy during operation.
|
Mechanical Vibration or Fan Imbalance | View Details |
| – |
Domestic hot water temperature fluctuates or runs out quickly on combi or indirect systems
|
Inconsistent Domestic Hot Water Production | View Details |
| – |
Radiators heat unevenly; some are hot while others remain cool.
|
Uneven Heat Distribution | View Details |
No matching codes found
Advertisements