Boiler not heating: a winter no-heat checklist before calling for repair
A practical checklist for hydronic or boiler heating problems without opening or bypassing heating equipment.
Updated September 28, 2026Describe what has stopped working
A boiler call is easier to triage when you distinguish whole-building no heat from a single cold zone. Note thermostat settings, whether the boiler appears powered, visible fault codes, unusual noise and whether domestic hot water is also affected if the system provides it.
Do not open fuel or pressure components
Homeowner checks should stay non-invasive. Do not bypass safety controls, open sealed combustion components or attempt pressure adjustments unless the manufacturer’s instructions specifically call for a user procedure you understand.
Escalate safety symptoms immediately
Fuel smells, visible leaking near electrical components or a carbon-monoxide alarm change the response. Ontario guidance says to leave immediately and call emergency services from outside when a CO alarm sounds.