E07
Mysa Load Detection / Zero-Cross Circuit Failure

Thermostat displays E07 and cannot detect or control the connected heater load.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Open circuit between thermostat LOAD terminals and heater, Loose wire connection at thermostat or junction box, Failed zero-cross detection circuit on main board

How to Fix / Troubleshooting

Safety first: Turn OFF the breaker and verify power is off before touching any wiring.

Steps to check:

  • Inspect thermostat wiring: Remove the thermostat and verify that the LOAD wires are firmly secured in the correct terminals. Re-strip and re-terminate if copper is oxidized or damaged.
  • Check continuity to heater: With power OFF, use a multimeter to check continuity from the thermostat LOAD wires to the heater terminals. An open circuit indicates a break in the cable or a loose connection in a junction box.
  • Verify heater resistance: Measure resistance across the heater element. An infinite reading indicates a failed (open) heater.
  • Reinstall and test: After correcting any wiring issues, restore power and see if E07 clears.

If wiring and heater are confirmed good but E07 persists, the internal load detection or zero-cross circuit on the main board is likely defective. Replace the thermostat.

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Repair Difficulty

Hard 4/5

Required Part

Main Control Board (Load Detection / Zero-Cross Circuit)
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