Tesy
Tesy Water Heaters Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E01
Digital Tesy water heater does not heat; display shows E01 shortly after power‑up.
NTC Temperature Sensor Open Circuit
E02
Tesy water heater shows E02 and stops heating; sometimes trips safety thermostat.
NTC Temperature Sensor Short Circuit / Overtemperature Detection
E03
Tesy digital water heater shows E03 and does not heat; sometimes relay clicks but no temperature rise.
Heating Element Circuit Open / No Load Detected
E04
Tesy water heater displays E04 and stops; may occur after power surge or lightning.
Control Board Internal Error / EEPROM or MCU Fault
E05
Tesy heater shows E05; water temperature reading on display is clearly wrong (e.g., shows 0°C or 99°C constantly).
Secondary / Outlet Temperature Sensor Fault
E06
Tesy water heater shows E06 and does not respond to keypad or touch controls.
User Interface / Keypad Communication Error
E07
Tesy digital heater shows E07; unit may heat uncontrollably or not at all.
Triac / Power Relay Fault (Stuck ON or OFF)
E08
Tesy water heater shows E08; unit may not power up fully or may reset intermittently.
Low Voltage / Power Supply Error
E09
Tesy heater shows E09; water does not heat to set temperature or overshoots significantly.
Calibration / Temperature Control Error
E10
Tesy water heater shows E10; unit may shut down shortly after start, often associated with dry tank condition.
Dry-Fire / No Water in Tank Protection Triggered
E11
Tesy digital heater shows E11; unit may not respond to Wi‑Fi or smart control functions.
Communication Error with Wi‑Fi / Smart Module
E12
Tesy heater shows E12; anti-legionella or boost heating program fails to complete.
Anti-Legionella Cycle Failure
E13
Tesy water heater shows E13; unit may shut down with no obvious temperature issue.
Earth Leakage / Ground Fault Detection
E14
Tesy heater shows E14; unit may not reach set temperature and shuts down early.
Flow / Circulation Error (for models with circulation pump or external loop)
E15
Tesy heater shows E15; overheat protection has been triggered repeatedly.
Safety Thermostat Trip / Overtemperature Lockout
E16
Tesy heater shows E16; display may indicate sensor mismatch or configuration error after replacing parts.
Configuration / Sensor Type Mismatch
E17
Tesy heater shows E17; unit may not accept new settings or time programs.
Memory / RTC (Real-Time Clock) Error
E18
Tesy heater shows E18; unit may indicate sensor overrange or under-range conditions intermittently.
Intermittent Sensor / Wiring Fault
E19
Tesy heater shows E19; unit may not detect external control signal (e.g., tariff control, smart grid input).
External Control Input Error
Symptom
Condensation or water droplets forming on the outside of the heater.
Condensation Due to Temperature Difference
Symptom
Digital Tesy heater display works but buttons do not respond or respond erratically.
Faulty Keypad / Touch Panel
Symptom
Heater does not turn on after a power outage; no lights or display.
Power Supply / Control Board Failure After Surge
Symptom
Heater emits a metallic or rusty smell from hot water.
Anode Depletion / Internal Corrosion
Symptom
Heater makes loud popping or crackling noises during heating.
Limescale Build-Up on Heating Element
Symptom
Heater outer casing feels unusually hot to the touch.
Insulation Degradation or Local Overheating
Symptom
Heater produces rotten egg (sulfur) smell in hot water.
Bacterial Reaction with Magnesium Anode
Symptom
Heater vibrates or hums loudly when heating.
Mechanical Vibration / Resonance
Symptom
No hot water at taps, but heater tank is hot (confirmed by touch or drain).
Hot Water Outlet / Mixing Valve Obstruction
Symptom
Water dripping from the safety valve discharge pipe periodically.
Normal Expansion Drip or Overpressure Discharge
Symptom
Water hammer or banging noise in pipes when heater fills or stops drawing water.
Hydraulic Shock in Plumbing
Symptom
Water heater does not heat at all; no error code (mechanical thermostat model, indicator light off).
No Power to Heater / Open Circuit
Symptom
Water heater frequently runs out of hot water faster than expected.
Insufficient Capacity or Stratification Issue
Symptom
Water heater heats but trips the circuit breaker or RCD/GFCI intermittently.
Electrical Short or Earth Leakage
Symptom
Water heater indicator light is on but water remains lukewarm or cold.
Failed Heating Element
Symptom
Water heater leaks from the bottom cover or around the element flange.
Tank or Flange Gasket Leak
Symptom
Water temperature is excessively hot; risk of scalding at taps.
Thermostat Stuck Closed / Control Failure
Symptom
Water temperature is too low even when thermostat or setpoint is at maximum.
Thermostat Miscalibration or Sensor Drift
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Digital Tesy water heater does not heat; display shows E01 shortly after power‑up.
|
NTC Temperature Sensor Open Circuit | View Details |
| E02 |
Tesy water heater shows E02 and stops heating; sometimes trips safety thermostat.
|
NTC Temperature Sensor Short Circuit / Overtemperature Detection | View Details |
| E03 |
Tesy digital water heater shows E03 and does not heat; sometimes relay clicks but no temperature rise.
|
Heating Element Circuit Open / No Load Detected | View Details |
| E04 |
Tesy water heater displays E04 and stops; may occur after power surge or lightning.
|
Control Board Internal Error / EEPROM or MCU Fault | View Details |
| E05 |
Tesy heater shows E05; water temperature reading on display is clearly wrong (e.g., shows 0°C or 99°C constantly).
|
Secondary / Outlet Temperature Sensor Fault | View Details |
| E06 |
Tesy water heater shows E06 and does not respond to keypad or touch controls.
|
User Interface / Keypad Communication Error | View Details |
| E07 |
Tesy digital heater shows E07; unit may heat uncontrollably or not at all.
|
Triac / Power Relay Fault (Stuck ON or OFF) | View Details |
| E08 |
Tesy water heater shows E08; unit may not power up fully or may reset intermittently.
|
Low Voltage / Power Supply Error | View Details |
| E09 |
Tesy heater shows E09; water does not heat to set temperature or overshoots significantly.
|
Calibration / Temperature Control Error | View Details |
| E10 |
Tesy water heater shows E10; unit may shut down shortly after start, often associated with dry tank condition.
|
Dry-Fire / No Water in Tank Protection Triggered | View Details |
| E11 |
Tesy digital heater shows E11; unit may not respond to Wi‑Fi or smart control functions.
|
Communication Error with Wi‑Fi / Smart Module | View Details |
| E12 |
Tesy heater shows E12; anti-legionella or boost heating program fails to complete.
|
Anti-Legionella Cycle Failure | View Details |
| E13 |
Tesy water heater shows E13; unit may shut down with no obvious temperature issue.
|
Earth Leakage / Ground Fault Detection | View Details |
| E14 |
Tesy heater shows E14; unit may not reach set temperature and shuts down early.
|
Flow / Circulation Error (for models with circulation pump or external loop) | View Details |
| E15 |
Tesy heater shows E15; overheat protection has been triggered repeatedly.
|
Safety Thermostat Trip / Overtemperature Lockout | View Details |
| E16 |
Tesy heater shows E16; display may indicate sensor mismatch or configuration error after replacing parts.
|
Configuration / Sensor Type Mismatch | View Details |
| E17 |
Tesy heater shows E17; unit may not accept new settings or time programs.
|
Memory / RTC (Real-Time Clock) Error | View Details |
| E18 |
Tesy heater shows E18; unit may indicate sensor overrange or under-range conditions intermittently.
|
Intermittent Sensor / Wiring Fault | View Details |
| E19 |
Tesy heater shows E19; unit may not detect external control signal (e.g., tariff control, smart grid input).
|
External Control Input Error | View Details |
| – |
Condensation or water droplets forming on the outside of the heater.
|
Condensation Due to Temperature Difference | View Details |
| – |
Digital Tesy heater display works but buttons do not respond or respond erratically.
|
Faulty Keypad / Touch Panel | View Details |
| – |
Heater does not turn on after a power outage; no lights or display.
|
Power Supply / Control Board Failure After Surge | View Details |
| – |
Heater emits a metallic or rusty smell from hot water.
|
Anode Depletion / Internal Corrosion | View Details |
| – |
Heater makes loud popping or crackling noises during heating.
|
Limescale Build-Up on Heating Element | View Details |
| – |
Heater outer casing feels unusually hot to the touch.
|
Insulation Degradation or Local Overheating | View Details |
| – |
Heater produces rotten egg (sulfur) smell in hot water.
|
Bacterial Reaction with Magnesium Anode | View Details |
| – |
Heater vibrates or hums loudly when heating.
|
Mechanical Vibration / Resonance | View Details |
| – |
No hot water at taps, but heater tank is hot (confirmed by touch or drain).
|
Hot Water Outlet / Mixing Valve Obstruction | View Details |
| – |
Water dripping from the safety valve discharge pipe periodically.
|
Normal Expansion Drip or Overpressure Discharge | View Details |
| – |
Water hammer or banging noise in pipes when heater fills or stops drawing water.
|
Hydraulic Shock in Plumbing | View Details |
| – |
Water heater does not heat at all; no error code (mechanical thermostat model, indicator light off).
|
No Power to Heater / Open Circuit | View Details |
| – |
Water heater frequently runs out of hot water faster than expected.
|
Insufficient Capacity or Stratification Issue | View Details |
| – |
Water heater heats but trips the circuit breaker or RCD/GFCI intermittently.
|
Electrical Short or Earth Leakage | View Details |
| – |
Water heater indicator light is on but water remains lukewarm or cold.
|
Failed Heating Element | View Details |
| – |
Water heater leaks from the bottom cover or around the element flange.
|
Tank or Flange Gasket Leak | View Details |
| – |
Water temperature is excessively hot; risk of scalding at taps.
|
Thermostat Stuck Closed / Control Failure | View Details |
| – |
Water temperature is too low even when thermostat or setpoint is at maximum.
|
Thermostat Miscalibration or Sensor Drift | View Details |
No matching codes found
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