The heat stops working and the building gets cold fast. Before calling a licensed master plumber in New York City, a few basic checks can resolve the problem on their own — or at minimum tell you exactly what you’re dealing with before anyone shows up. Many of the most common reasons a boiler stops producing heat have nothing to do with the boiler itself, and working through the list below takes less than ten minutes.
If none of these resolve the issue, that’s useful information too. It tells you the problem is beyond a simple fix and that professional diagnosis is the right next step.
Check the Power Switch First
Boilers have a power switch — usually located on or near the boiler unit itself, or at the top of the basement stairs. It’s a standard toggle switch that looks similar to a light switch, and it gets turned off more often than most property owners realize — during cleaning, maintenance work, or simply by accident. Check that it’s in the on position before moving to anything else.
Check the Breaker or Fuse
Both gas and electric boilers have electrical components, which means both are subject to tripped breakers and blown fuses. Go to the electrical panel and look for any tripped breakers — a tripped breaker sits between the on and off positions rather than fully in either direction. Reset it by switching it fully off first and then back to on. If a fuse has blown, replace it with one of the same amperage rating.
A breaker that trips again immediately after being reset indicates a more significant electrical issue. At that point stop resetting it and call a professional.
Check the Thermostat
The thermostat is a more common culprit than most people expect. Check that it’s set to heat rather than cool, that the temperature setting is above the current room temperature, and that the system is set to auto or on rather than off. Turn the thermostat up to its highest setting and wait a few minutes to see if the boiler activates.
If the thermostat takes batteries, replace them. Low battery power produces erratic thermostat behavior including failure to send the signal that triggers the boiler to turn on. This is one of the simplest and cheapest fixes available when a heating system appears to have stopped working.
Check the Fuel Source
For gas-powered boilers, confirm that the gas supply valve on the boiler is open. The valve is open when the handle is parallel to the pipe and closed when it’s perpendicular. If the valve was recently closed — during service work or as a precaution — and wasn’t reopened, no gas is reaching the burner.
Also check whether other gas appliances in the building are working. If a stove or hot water heater is also not receiving gas, the issue may be with the gas supply to the building rather than with the boiler specifically. In that case, contact ConEd or National Grid to check service to the property.
Check the Pilot Light
Gas boilers use a pilot light to ignite the burner. There are two types — manual ignition and automatic ignition — and most boilers are labeled to indicate which type they have.
Automatic ignition pilot lights relight themselves when the thermostat calls for heat. If the pilot light on an automatic ignition boiler has gone out, the boiler will typically display an error code or indicator light. Consult the boiler’s manual or the label on the unit for what that code means and whether relighting is something the manufacturer recommends doing independently.
Manual ignition pilot lights need to be lit manually — typically at the start of the heating season in the fall — and can go out due to a draft, a brief interruption in gas supply, or other factors. Most boilers with manual ignition include step-by-step relighting instructions on a label attached to the unit. Follow those instructions carefully. If you smell gas at any point during the process, stop immediately, leave the area, and contact the gas utility.
A pilot light that won’t stay lit after relighting indicates a problem with the thermocouple — the safety device that senses whether the pilot is burning and keeps the gas valve open. Thermocouple replacement is a professional repair.
When Self-Troubleshooting Ends
These five checks resolve a significant number of heating complaints without any professional involvement. When they don’t resolve the issue, the cause is beyond what basic troubleshooting can address — and continuing to probe without the right tools and knowledge risks making things worse.
A boiler that has power, fuel, a functioning thermostat, and an active pilot light but still isn’t producing heat may have a faulty zone valve, a failing pump, a pressure problem, a cracked heat exchanger, or a control board issue. Each of these requires professional diagnosis and repair.
Empire Plumbing is a licensed master plumber in New York City providing boiler inspections and boiler repair services across Brooklyn, Manhattan, Staten Island, Queens, and the Bronx. If your heating system isn’t working and the basic checks haven’t resolved it, call Gary at (718) 494-7301 or (917) 642-3041 to diagnose and fix the problem.