Error Code	Symptom	Fault Type	Guide
E01	Control panel displays E01 and the softener does not start a regeneration cycle	Inlet Water Supply Fault	View Details
E02	Display shows E02 and the unit fails to draw brine during regeneration	Brine Draw / Injector Blockage	View Details
E03	E03 displayed and the softener does not refill the brine tank at the end of regeneration	Brine Refill / Refill Valve Fault	View Details
E04	E04 error and the display indicates a motor or valve position fault	Control Valve Motor / Cam Position Error	View Details
E05	E05 displayed and the unit reports a flow sensor or meter error	Flow Meter / Turbine Sensor Failure	View Details
E06	E06 error and the softener shows incorrect or no salt level reading (on models with electronic salt sensor)	Salt Level Sensor Fault	View Details
E07	E07 displayed and the unit indicates a drain or backwash fault	Drain Line / Backwash Flow Restriction	View Details
E08	E08 error and the display shows a high water level or brine tank overflow warning	Brine Tank Overfill / Float Valve Failure	View Details
E09	E09 displayed and the unit reports a resin tank pressure or leak fault (on models with pressure sensor)	Internal Pressure / Leak Detection Error	View Details
E10	E10 error and the display shows a general electronics or PCB fault	Control PCB / Firmware Error	View Details
E11	E11 displayed and the clock or regeneration time will not hold settings	Real-Time Clock / Memory Backup Fault	View Details
E12	E12 error and the unit indicates a sensor calibration or configuration fault	Configuration / Parameter Error	View Details
E13	E13 displayed and the unit reports a temperature sensor or over-temperature fault (on models with temperature monitoring)	Temperature Sensor Error	View Details
E14	E14 error and the unit indicates a twin-cylinder changeover fault (on duplex Monarch models)	Cylinder Changeover / Shuttle Valve Error	View Details
E15	E15 displayed and the unit reports an internal communication error between display and main board	Internal Communication / Bus Error	View Details
E16	E16 error and the unit indicates an excessive regeneration frequency or capacity calculation fault	Abnormal Regeneration Frequency	View Details
E17	E17 displayed and the unit reports low salt or salt not detected despite salt being present	Salt Detection / Low Salt Alarm Fault	View Details
E18	E18 error and the unit indicates a brine concentration or conductivity fault (on models with brine sensor)	Brine Concentration / Conductivity Sensor Error	View Details
E19	E19 displayed and the unit reports an internal valve seal pack or piston travel error	Valve Piston / Seal Pack Travel Fault	View Details
E20	E20 error and the unit indicates an external leak or tray sensor activation (on cabinet models with base sensor)	Cabinet Base Leak Detection	View Details
–	Brine tank full of water and not draining during regeneration	Brine Tank Flooding / No Brine Draw	View Details
–	Display is completely blank; softener appears dead	No Power to Control Panel	View Details
–	Display is on but buttons do not respond or respond intermittently	Keypad / Button Failure	View Details
–	Softener appears to work but hot water remains scaled or hard	Partial Softening / Incorrect Plumbing	View Details
–	Softener cabinet or surrounding area smells strongly of damp or mould	Cabinet Moisture / Poor Ventilation	View Details
–	Softener causes intermittent bursts of cloudy or milky water	Air Entrapment / Microbubbles	View Details
–	Softener causes noticeable drop in water pressure throughout the house	Flow Restriction Through Softener	View Details
–	Softener does not regenerate at all; display is on but no cycles occur	No Regeneration / Control Scheduling Fault	View Details
–	Softener emits a constant humming or buzzing noise from the valve head	Valve Motor or Transformer Hum	View Details
–	Softener emits a rotten egg or foul odour from softened water	Bacterial Growth in Resin Bed or Brine Tank	View Details
–	Softener installed but no water flows through it (no supply to house)	Installation / Valve Configuration Error	View Details
–	Softener makes loud banging or hammering noises during regeneration	Water Hammer / Rapid Valve Closure	View Details
–	Softener produces a clicking or ratcheting noise during regeneration	Gear Train Wear / Cam Misalignment	View Details
–	Softener regenerates too often, wasting salt and water	Over-Regeneration / Oversized Hardness Setting	View Details
–	Softener stuck in regeneration and does not return to service mode	Regeneration Cycle Hang	View Details
–	Softener uses excessive salt; brine tank empties quickly	Over-Brining / Excessive Salt Consumption	View Details
–	Softener uses very little or no salt; salt level hardly drops over weeks	No Brine Draw / Under-Brining	View Details
–	Softener water has a salty taste at taps after regeneration	Residual Brine Carryover	View Details
–	Water remains hard at taps even though the Monarch softener appears to run normally (no error code)	Loss of Softening Capacity	View Details
–	Water softener leaking from around the control valve or resin tank neck	Valve-to-Tank Seal Leak	View Details
–	Water softener leaking from drain hose connection or during backwash	Drain Connection Leak	View Details

Monarch Water Softeners Error Codes

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