Why Is My Boiler Not Heating? Causes & 4 DIY Checks
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Lancaster County runs on boilers - oil and gas units feeding radiators in rowhomes, farmhouses, and older borough properties. When one stops heating, the cause is usually one of a handful of things: a thermostat problem, lost power, low system pressure, a pilot or ignition failure, or air trapped in the radiators. The checks below are safe for any homeowner. What's not safe: opening burner compartments, working on gas lines, or repeatedly repressurizing a system that keeps losing pressure - that's leak territory, and it needs a professional.
HOW TO TROUBLESHOOT A BOILER THAT ISN'T HEATING
Check the thermostat. Set the thermostat to HEAT and above room temperature, and replace the batteries if needed. On zoned systems, check the thermostat for the cold zone specifically.
Confirm power. Make sure the boiler's power switch is on and the breaker hasn't tripped. Boilers have a service switch that looks like a light switch, often at the top of the basement stairs.
Check the pressure gauge. If boiler pressure is low (below about 12 psi), repressurize using the filling loop per your manual. A system that needs repressurizing repeatedly is losing water somewhere - stop and call at that point.
Check the pilot or ignition. Confirm the pilot light is lit or the electronic ignition is firing; relight per the manufacturer's instructions. If the pilot won't stay lit, the thermocouple is a likely suspect and needs service.
Bleed the radiators. If some radiators stay cold, bleed trapped air so hot water can circulate evenly. Cold-at-the-top radiators are the classic trapped-air signature.
Call a professional. If the boiler still won't heat, a failed circulator pump, valve, or control needs service. Call Boro Mechanical at 717-517-6120.
Boiler still cold? Oil or gas, New Yorker or NTI or anything else - we service the boilers other contractors won't touch. Why your boiler isn't heating is our specialty, not our side job.
A decades-old oil boiler isn't a reason to panic - well-maintained cast-iron boilers routinely outlast the contractors who install them. But they do need someone who knows oil heat: burner tuning, nozzle and filter changes, soot management, and honest end-of-life judgment. Boro Mechanical is NORA Silver certified and services oil heating systems across Lancaster County every week, including the older New Yorker and NTI units common in this area. If your no-heat problem turned out to be furnace-side instead, see the furnace troubleshooting steps, or browse the full resources hub.
FREQUENTLY ASKED QUESTIONS
The usual causes are a thermostat not calling for heat, a tripped breaker or switched-off service switch, low water pressure, or a pilot/ignition failure. Check those four in order. If the boiler has power, pressure, and a working pilot but still won't fire, the aquastat, circulator, or controls need professional diagnosis - call 717-517-6120.
The problems we see most are low system pressure from small leaks, trapped air leaving radiators cold, failed circulator pumps, pilot and ignition faults, and on oil boilers, clogged nozzles and filters from skipped maintenance. Most are inexpensive to fix when caught early, which is why an annual service visit pays for itself.
Once a year, ideally in late summer or fall before heating season. Annual service covers burner cleaning and tuning, safety checks, and on oil boilers the nozzle and filter changes that prevent most winter breakdowns. Older systems especially benefit - a tuned boiler burns less fuel and fails far less often. Boro Mechanical offers maintenance plans that cover it.
GET YOUR RADIATORS HOT AGAIN
Priority no-heat response with same-day service during business hours whenever possible - from the NORA Silver certified boiler specialists Lancaster County's older homes rely on.
