What should I do if my boiler will not turn on or is locked out?

What this symptom usually means

A boiler that will not turn on or shows a lockout is not just “not heating.” It is a specific failure of the startup sequence. The control is either not getting power, is seeing an unsafe condition such as low water or blocked venting, or is trying to light the burner and failing enough times that it shuts itself down to prevent damage or unsafe operation.

What you can tell from the way it acts

A completely silent boiler with a blank display points first to power loss at the breaker, service switch, fuse, transformer, or control board. If the display is lit and shows a code, that code often separates low pressure, ignition lockout, venting faults, and limit or sensor problems. If you hear clicking, humming, or a fan starting but no steady burner operation, that leans more toward ignition failure, flame sensing, condensate blockage, or another safety interlock stopping the sequence.

Your pressure gauge gives another important clue that is specific to lockout complaints. On many residential hot-water boilers, cold system pressure is often around 12 to 15 psi; if it is well below that, the low-water safety may prevent firing. If a breaker is tripped and trips again after being reset, stop there and arrange service rather than forcing more restart attempts.

What a technician typically checks on a no-start or lockout boiler call

A service visit usually starts with confirming line voltage, fuse condition, service switch position, and whether the control board is powered. From there the technician reads stored fault codes, checks system pressure and the pressure-reducing feed setup, tests safeties such as the low-water cutoff and limits, and watches an actual call for heat to see where the sequence stops. If the boiler starts then drops out, the next checks are commonly ignition components, flame signal, vent proving, condensate drainage on condensing models, and control board outputs.

What affects repair cost

Cost depends heavily on whether this is a simple power or pressure issue or a component failure inside the ignition and safety chain. Typical 2025-2026 US repair ranges are often about $150-$350 for a basic diagnostic and minor electrical or reset-related fix, roughly $200-$600 for pressure-related parts, sensors, or low-water cutoff issues, and about $300-$1,200+ for ignition modules, control boards, inducer-related parts, or vent/condensate corrections on modern boilers. Brand-specific parts, after-hours timing, and whether the boiler is easily accessible can change the total.

Avoid repeated manual resets if the boiler keeps locking out after one restart. One lockout can be a nuisance trip; repeated lockouts usually mean the boiler is failing a safety check or burner-lighting step, and repeated attempts can worsen wear on ignition parts and leave you without heat at the worst time.