Thermostat shows E6 and cannot detect or control the wireless receiver or wiring centre.

Safety first: While RF troubleshooting is low risk, any work on the receiver or wiring centre involves mains voltage. Turn off power to the receiver before opening its cover.

Steps to diagnose and fix:

• 1. Check receiver power: Verify that the Danfoss receiver or wiring centre has power (status LED on, boiler or actuator wiring intact). Reset its power by switching off for 30 seconds and back on.
• 2. Reduce interference: Move the thermostat closer to the receiver (within a few metres) and away from large metal objects, Wi‑Fi routers, or thick concrete walls. See if E6 clears.
• 3. Re-pair devices: Follow the Danfoss pairing procedure for your model (often involves pressing a pairing button on the receiver and selecting "pair" in the thermostat menu). Confirm that the receiver acknowledges pairing (LED change or beep).
• 4. Check RF settings: Ensure the thermostat is configured for the correct zone/channel if using a Danfoss multi-zone wiring centre. Misconfigured zone IDs can appear as communication errors.
• 5. Test with another thermostat or receiver: If available, pair a known-good Danfoss thermostat to the receiver, or pair the thermostat to another receiver, to isolate which device has the RF fault.
• 6. Replace faulty RF component: If the RF module is integrated, replace the thermostat or receiver unit. If it is a plug-in RF module, install a new Danfoss RF module compatible with your system.

When to call a professional: If pairing repeatedly fails and wiring centre power/wiring is suspect, a heating technician should inspect the installation.