Thermostat displays E7 and cannot connect to heating system; app may show valve/boiler control error.

Safety first: Turn off power to both the thermostat and boiler/valve control circuits.

Steps:

• Verify control wiring: Check that the thermostat's control output terminals (e.g., COM and NO for dry contact, or OUT for 230 V switched live) are wired exactly as shown in the Meross wiring diagram for your boiler or valve type.
• Check continuity: With power off, disconnect the control wires at the boiler/valve end and measure continuity from thermostat to boiler. Repair any breaks or loose connections.
• Confirm control type: Ensure you are not feeding mains voltage into a dry-contact input on the boiler, or vice versa. Miswiring can trigger E7 and damage the control circuit.
• Test with a simple load: Temporarily connect a test lamp or small resistive load to the thermostat output to confirm it switches correctly when calling for heat. If E7 persists and the output does not change, the internal control circuit is faulty.

Outcome: Correct wiring issues or replace the thermostat if the control output cannot be restored.