Error Code	Symptom	Fault Type	Guide
AIR	Controller displays AIR or AIRLOCK and solar heating cycles on and off; gurgling noises are heard from the roof.	Air Entrapment in Heliocol Collector Array	View Details
CAL	Controller displays CAL or CALIB and temperature readings are obviously incorrect; system may not start or may overheat.	Controller Calibration Mode or Corrupted Temperature Calibration	View Details
COM	Controller displays COM or COMM and does not respond to automation commands from the main pool control system.	Communication Link Failure Between Solar Controller and Pool Automation	View Details
ERR	Controller displays ERR or ERROR with no additional code and solar heating is locked out.	General Controller Fault / Internal Self-Test Failure	View Details
FLO	Controller displays FLO or FLOW and solar heating will not start even when the pump is running.	Insufficient Water Flow Through Solar Collector Array	View Details
FRZ	Controller displays FRZ or FREEZE and forces circulation through the Heliocol panels even when heating is off.	Freeze Protection Mode Activation	View Details
HI	Controller displays HI or HIGH TEMP and shuts off solar heating even though the pool does not feel excessively hot.	Over-Temperature Sensor Reading / Sensor Drift	View Details
HIGHP	Controller displays HIGHP or HIGH PRESS and disables solar heating; filter pressure is significantly above normal.	High System Pressure / Restricted Flow	View Details
LO	Controller displays LO or LOW TEMP and refuses to open the solar valve even on warm sunny days.	Under-Temperature Sensor Reading / Shaded Sensor	View Details
LOWP	Controller displays LOWP or LOW PRESS and shuts off solar heating; filter pressure gauge reads unusually low.	Low System Pressure / Pump Priming Issue	View Details
PMP	Controller displays PMP or PUMP and solar heating is disabled; controller indicates no pump operation even though the pump may be running.	Pump Interlock or Relay Feedback Fault	View Details
POOL	Controller flashes POOL or POOL SEN and will not allow solar heating; pool temperature reading is blank or unrealistic.	Pool Water Temperature Sensor Fault	View Details
SEN	Controller displays SEN or SENSOR and solar heating is disabled even on sunny days.	Solar Temperature Sensor Fault	View Details
SLO	Controller displays SLO or SLOW RISE and shuts off solar heating because the pool temperature is not increasing as expected.	Insufficient Solar Heat Gain / Performance Fault	View Details
VAL	Controller displays VAL or VALVE and the solar valve does not move when solar heat is requested.	Solar Diverter Valve Actuator Fault	View Details
–	Dripping or small puddle of water inside or directly under the solar controller enclosure.	Water Intrusion into Controller Housing	View Details
–	Gurgling or sloshing sounds from roof and intermittent flow to Heliocol panels during operation.	Intermittent Air Ingress into Solar Loop	View Details
–	Heliocol panels show visible cracks or splits in the riser tubes or manifolds, with or without active leaks.	Panel Structural Damage	View Details
–	Loud banging or water hammer noise in pipes when solar turns on or off.	Water Hammer in Solar Plumbing Circuit	View Details
–	Noticeable drop in overall pool circulation flow whenever solar is activated.	Excessive Flow Restriction Through Heliocol Array	View Details
–	Persistent dripping or spraying from vacuum relief valve at the top of the Heliocol array.	Leaking Vacuum Relief Valve	View Details
–	Pool does not heat adequately even on sunny days; solar system appears to run normally with no error codes.	Underperforming Solar Heating System	View Details
–	Pool pump loses prime or cavitates when solar turns on; visible air in pump basket.	Excessive Suction Head or Improper Solar Plumbing Layout	View Details
–	Solar controller display is blank or intermittently turns off while pump continues to run.	Controller Power Loss or Intermittent Power Supply	View Details
–	Solar controller display is on but buttons do not respond or menus cannot be changed.	Controller Keypad or Interface Failure	View Details
–	Solar controller frequently resets or reboots when pump or other large loads turn on.	Electrical Noise or Voltage Drop Affecting Controller	View Details
–	Solar heating never turns on even when pool is below setpoint and roof is hot; no error codes displayed.	Improper Controller Configuration or Setpoint Settings	View Details
–	Solar heating only works when pump is in high-speed mode; in low-speed mode, solar never activates.	Inadequate Flow at Low Pump Speed for Solar Operation	View Details
–	Solar heating turns on and off rapidly (short cycling) even under steady sunny conditions.	Unstable Control Due to Sensor Placement or Settings	View Details
–	Solar system runs at night or on cloudy days, cooling the pool instead of heating it.	Incorrect Sensor Placement or Wiring Reversal	View Details
–	Solar valve actuator runs but stops in the wrong position, sending water to the roof when solar is off or bypassing panels when solar is on.	Misaligned Solar Valve Actuator	View Details
–	Strong plastic or burning smell near equipment pad when solar engages.	Overheating Electrical Component in Solar Control Circuit	View Details
–	Visible algae growth or staining on Heliocol panels and roof area around them.	Biological Growth on Panels Affecting Performance	View Details
–	Visible sagging or bowing of Heliocol panels between roof attachment points.	Insufficient Panel Support / Mounting Hardware Failure	View Details
–	Water leaking from Heliocol panel headers or manifold connections on the roof during pump operation.	Panel Header or Manifold Connection Leak	View Details
–	Water leaking from PVC plumbing near the solar feed or return lines at the equipment pad.	Solar Feed/Return Plumbing Leak at Equipment Pad	View Details

Heliocol Pool Heaters Error Codes

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