How to Fix / Troubleshooting

Safety: Turn off power before working on low-voltage wiring.

Check thermostat: Confirm the thermostat is set to heat mode and above room temperature. Replace batteries if applicable.
Inspect wiring: At the boiler, check the thermostat or TT terminals on the Crown control. Ensure wires are secure and not corroded.
Bypass test: With power off, temporarily jumper the TT terminals. Restore power; if the boiler starts, the issue is in the thermostat or wiring.
External controls: If a zone control panel is used, verify it has power and is indicating a call for heat to the boiler.

Boiler does not respond to thermostat; stays off even when there is a call for heat

Possible Causes