Thermostat shows E10 and indicates low supply voltage or power fault.

Safety first: Turn off power at the fused spur before removing the thermostat or accessing wiring.

Steps to diagnose:

• 1. Check backplate connections: Remove the thermostat from its base and ensure all low-voltage terminals are tight and wires are fully inserted.
• 2. Inspect cable: Follow the low-voltage cable from boiler or receiver to the thermostat. Look for crushed, cut, or overheated sections.
• 3. Measure supply voltage: With power on and using a multimeter (if competent), measure the voltage at the thermostat terminals. Compare with the specified range in the Baxi manual (e.g. 24 V DC or specific low-voltage range).
• 4. Check power source: If a plug-in power adapter is used, test it with a multimeter or substitute a known-good Baxi-approved adapter.

When to call a professional: If supply voltage is correct but E10 persists, the internal regulator or power circuit is likely faulty and the thermostat should be replaced.