Hayward
Hayward Pool Heaters Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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AGS
Heater shows AGS and locks out; no heating occurs.
Automatic Gas Shutoff Fault
AO
Display shows AO; blower may run continuously or not start; heater will not fire.
Air Flow / Air Pressure Switch Open
AO / AF
Heater intermittently shows AO or AF and shuts down during operation, especially in windy conditions.
Intermittent Combustion Air Fault
AO / PS
Heater shows AO or PS and shuts down when pump turns off; may chatter on/off at pump transitions.
Pressure Switch Transition Fault
bD
Display shows bD; heater will not fire when controlled by external automation.
Bypass or External Control Error
CE
Display shows CE and heater will not respond to temperature changes or calls for heat.
Communication Error Between Control Board and Display/Interface
EE
Heater display shows EE and is unresponsive; no heating occurs.
General Control Board Error
FS
Heater displays FS and will not fire; may occur after ignition attempt.
Flame Sense Fault
H5
Heater shows H5 and shuts down; may occur after running for a short period.
High-Temperature Lockout / Repeated High Limit Trips
HLS
Heater displays HLS and will not fire; may occur immediately on call for heat.
High Limit Switch Open
HS
Heater displays HS and will not fire or shuts down shortly after starting; unit may feel very hot near the outlet manifold.
High-Temperature Sensor Trip
IF
Heater will not ignite; display shows IF shortly after a call for heat; blower may run but no flame is established.
Ignition Failure Lockout
IGN
Display shows IGN or ignition error; heater attempts to start but shuts down quickly.
Ignition Sequence Failure
LO
Heater display shows LO and will not fire; water is circulating but heater does not start.
Low Water Flow / Pressure Fault
LO / FLO
Heater intermittently shows LO or FLO and cycles on and off; sometimes heats briefly then shuts down.
Intermittent Flow Sensing Fault
LO / HLS
Heater alternates between LO and HLS; unit short-cycles and water temperature rises slowly.
Flow-Related Overheat Cycling
ROL
Heater displays ROL or rollout error; unit locks out and will not fire.
Flame Rollout Safety Trip
ROL / AGS
Heater shows ROL or AGS after running for a short time; strong smell of exhaust near unit.
Overheat and Flame Rollout Combination Fault
Sb
Display shows Sb; heater does not respond to normal temperature adjustments.
Service/Standby Mode Active
SFS
Heater shows SFS; unit will not fire or shuts down quickly.
Stack Flue Sensor Fault
SNS
Heater displays SNS; temperature readings are erratic or incorrect.
Water Temperature Sensor Fault
Symptom
Condensation or water dripping from vent or flue, especially in cool weather.
Condensation in Vent System
Symptom
Display shows normal operation but heater shuts down when wind gusts hit the vent area.
Wind-Induced Flame or Draft Disruption
Symptom
Heater cabinet is excessively hot to the touch on sides or top during operation.
Abnormal Radiant Heat / Insufficient Ventilation
Symptom
Heater cycles on and off rapidly (short cycling) without reaching set temperature.
Short Cycling Control or Flow Issue
Symptom
Heater display flickers or resets when pump or other equipment turns on.
Electrical Interference or Voltage Drop
Symptom
Heater display is on but does not respond to button presses; cannot change temperature or mode.
Unresponsive User Interface
Symptom
Heater emits a high-pitched whine or grinding noise from the blower area.
Blower Motor or Bearing Failure
Symptom
Heater leaks water from the bottom of the cabinet during or after operation.
Internal Water Leak
Symptom
Heater makes loud banging or knocking noises during operation, especially at startup.
Water Hammer / Boiling in Heat Exchanger
Symptom
Heater runs but water does not reach set temperature; very slow heating or no noticeable temperature rise.
Insufficient Heat Output
Symptom
Heater shuts off when spa jets are turned on or when valves change position.
Flow Interruption Due to Valve Operation
Symptom
Heater turns on even when thermostat is set low or off; water overheats.
Thermostat or Control Relay Stuck Closed
Symptom
Heater will not start at all; display is blank and no lights or sounds are present.
No Power to Heater
Symptom
Rust-colored water or staining around heater base; corrosion visible on metal components.
Corrosion and Rust Damage
Symptom
Soot or black staining on top of heater or around vent outlet.
Sooting / Incomplete Combustion
Symptom
Strong gas smell near heater, especially during or after ignition attempts.
Gas Leak or Incomplete Ignition
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| AGS |
Heater shows AGS and locks out; no heating occurs.
|
Automatic Gas Shutoff Fault | View Details |
| AO |
Display shows AO; blower may run continuously or not start; heater will not fire.
|
Air Flow / Air Pressure Switch Open | View Details |
| AO / AF |
Heater intermittently shows AO or AF and shuts down during operation, especially in windy conditions.
|
Intermittent Combustion Air Fault | View Details |
| AO / PS |
Heater shows AO or PS and shuts down when pump turns off; may chatter on/off at pump transitions.
|
Pressure Switch Transition Fault | View Details |
| bD |
Display shows bD; heater will not fire when controlled by external automation.
|
Bypass or External Control Error | View Details |
| CE |
Display shows CE and heater will not respond to temperature changes or calls for heat.
|
Communication Error Between Control Board and Display/Interface | View Details |
| EE |
Heater display shows EE and is unresponsive; no heating occurs.
|
General Control Board Error | View Details |
| FS |
Heater displays FS and will not fire; may occur after ignition attempt.
|
Flame Sense Fault | View Details |
| H5 |
Heater shows H5 and shuts down; may occur after running for a short period.
|
High-Temperature Lockout / Repeated High Limit Trips | View Details |
| HLS |
Heater displays HLS and will not fire; may occur immediately on call for heat.
|
High Limit Switch Open | View Details |
| HS |
Heater displays HS and will not fire or shuts down shortly after starting; unit may feel very hot near the outlet manifold.
|
High-Temperature Sensor Trip | View Details |
| IF |
Heater will not ignite; display shows IF shortly after a call for heat; blower may run but no flame is established.
|
Ignition Failure Lockout | View Details |
| IGN |
Display shows IGN or ignition error; heater attempts to start but shuts down quickly.
|
Ignition Sequence Failure | View Details |
| LO |
Heater display shows LO and will not fire; water is circulating but heater does not start.
|
Low Water Flow / Pressure Fault | View Details |
| LO / FLO |
Heater intermittently shows LO or FLO and cycles on and off; sometimes heats briefly then shuts down.
|
Intermittent Flow Sensing Fault | View Details |
| LO / HLS |
Heater alternates between LO and HLS; unit short-cycles and water temperature rises slowly.
|
Flow-Related Overheat Cycling | View Details |
| ROL |
Heater displays ROL or rollout error; unit locks out and will not fire.
|
Flame Rollout Safety Trip | View Details |
| ROL / AGS |
Heater shows ROL or AGS after running for a short time; strong smell of exhaust near unit.
|
Overheat and Flame Rollout Combination Fault | View Details |
| Sb |
Display shows Sb; heater does not respond to normal temperature adjustments.
|
Service/Standby Mode Active | View Details |
| SFS |
Heater shows SFS; unit will not fire or shuts down quickly.
|
Stack Flue Sensor Fault | View Details |
| SNS |
Heater displays SNS; temperature readings are erratic or incorrect.
|
Water Temperature Sensor Fault | View Details |
| – |
Condensation or water dripping from vent or flue, especially in cool weather.
|
Condensation in Vent System | View Details |
| – |
Display shows normal operation but heater shuts down when wind gusts hit the vent area.
|
Wind-Induced Flame or Draft Disruption | View Details |
| – |
Heater cabinet is excessively hot to the touch on sides or top during operation.
|
Abnormal Radiant Heat / Insufficient Ventilation | View Details |
| – |
Heater cycles on and off rapidly (short cycling) without reaching set temperature.
|
Short Cycling Control or Flow Issue | View Details |
| – |
Heater display flickers or resets when pump or other equipment turns on.
|
Electrical Interference or Voltage Drop | View Details |
| – |
Heater display is on but does not respond to button presses; cannot change temperature or mode.
|
Unresponsive User Interface | View Details |
| – |
Heater emits a high-pitched whine or grinding noise from the blower area.
|
Blower Motor or Bearing Failure | View Details |
| – |
Heater leaks water from the bottom of the cabinet during or after operation.
|
Internal Water Leak | View Details |
| – |
Heater makes loud banging or knocking noises during operation, especially at startup.
|
Water Hammer / Boiling in Heat Exchanger | View Details |
| – |
Heater runs but water does not reach set temperature; very slow heating or no noticeable temperature rise.
|
Insufficient Heat Output | View Details |
| – |
Heater shuts off when spa jets are turned on or when valves change position.
|
Flow Interruption Due to Valve Operation | View Details |
| – |
Heater turns on even when thermostat is set low or off; water overheats.
|
Thermostat or Control Relay Stuck Closed | View Details |
| – |
Heater will not start at all; display is blank and no lights or sounds are present.
|
No Power to Heater | View Details |
| – |
Rust-colored water or staining around heater base; corrosion visible on metal components.
|
Corrosion and Rust Damage | View Details |
| – |
Soot or black staining on top of heater or around vent outlet.
|
Sooting / Incomplete Combustion | View Details |
| – |
Strong gas smell near heater, especially during or after ignition attempts.
|
Gas Leak or Incomplete Ignition | View Details |
No matching codes found
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