Radiator controlled by Danfoss Ally thermostat stays cold even when the app and thermostat show a high setpoint and 'heating' demand.

Safety first: Radiator valves can be hot. Allow the radiator to cool if necessary and be cautious of hot water systems.

Steps:

• Check other radiators: If all radiators are cold, the boiler or circulation pump may be off or faulty; check boiler controls and pressure.
• Remove Ally head: Take off the Danfoss Ally radiator thermostat and inspect the valve pin. Press it in and out several times to free it if stuck.
• Verify adapter: Ensure the correct Danfoss adapter is used and tightened properly so the thermostat can fully push the valve pin.
• Recalibrate: Refit the Ally head, insert fresh batteries if needed, and run the valve calibration routine.
• Test heat: Set a high temperature and wait 15–30 minutes to see if the radiator warms up. If not, the valve body itself may be blocked and require replacement by a heating technician.