Syracuse averages 57.5 nights a year at or below 20F, so a furnace that quits does not leave much time to wonder. Work through the checks below in order. They cost nothing and each one rules out a cause the contractor would otherwise have to chase first.
Start with the thermostat
Confirm the mode is set to heat and the target is at least five degrees above the room temperature. If the screen is blank or dim, replace the batteries. A programmable thermostat can also revert to an old schedule after a power flicker, so look at the schedule, not just the mode.
Swapping in a second thermostat or tracing the wiring is a job for a contractor. Do not strip wires on a hunch.
Find the furnace switch and the breaker
Every furnace has an on and off switch that looks like an ordinary light switch, usually on the unit itself or on a nearby wall or joist. It gets knocked off during basement cleanups more often than people admit. Check it, and check the breaker panel for a tripped breaker labeled for the furnace.
If the breaker trips again right after you reset it, stop. Something is drawing too much current, and repeated resets will not cure that.
Look at the air filter
A filter packed with dust restricts airflow. The furnace heats up faster than the air can carry the heat away, and the limit switch shuts the burners off to protect the unit. Pull the filter out and hold it to the light. If you cannot see through it, replace it.
Condensate on high-efficiency furnaces
High-efficiency furnaces make water as they run and drain it through a plastic line. If that drain clogs or freezes, a float switch stops the furnace. New York's residential code also requires an auxiliary drain pan under a condensing furnace where a drain stoppage would damage the building, unless the furnace shuts itself down on a stoppage. So a furnace that stops on a blocked drain is not a nuisance to override. It is a protection doing its job.
A furnace that lights and quits is following a rule
New York's residential code requires every fuel gas space heater in a home to shut off the fuel when the flame goes out. If your furnace lights, runs for a few seconds and stops, the flame sensor or the flame itself is the question. It is usually a dirty sensor or a weak igniter, and a contractor can clean or replace it in a single visit. Nobody should defeat the safeguard to keep the furnace running.
What to try once, and what not to
- If the furnace or boiler shut itself off, leave it off. Do not reset or relight it. Book the repair. If you smell gas or an alarm sounds, leave first. Then call 911 or the gas utility from outside.
- Do not remove panels or bypass switches to make it run.
- Do not use an oven or a gas stove to heat the house.
When to stop and get everyone outside
Gas smell or a sounding carbon monoxide alarm: leave the house, then call 911 or the gas utility from outside. Smoke: leave and call 911 from outside. A brief dusty smell when the heat first runs each season is normal. A burning smell that lasts means switch the system off and book.
National Grid tells customers who smell gas anywhere, including in the home, to go outside and report it right away to 911 or its emergency center rather than assume someone else has called. The state Health Department says carbon monoxide is colorless and odorless and can kill before a person notices it. Repairs come afterward.
What to tell the contractor
The more precise the description, the faster the diagnosis. Note what you checked and what you saw. These details help most:
- Whether the blower runs and the air is cold, or nothing runs at all.
- Whether you hear clicking, humming or a rushing sound at start-up.
- Any error code blinking on the furnace board, visible through the small door or window.
- The age of the furnace and when it was last serviced.
If you rent
In Syracuse city, the code expects occupied buildings to stay at 68 degrees, measured two feet in from outside walls and five feet up, from September 15 to May 31 on days under 55 outdoors. The owner is responsible for adequate heat, except in units with their own heating systems. Tell your landlord promptly and in writing, and keep a copy. The guide on who pays covers the next steps.
When it is a repair
If every check passes and the furnace still will not heat, you have narrowed the problem to a part. That is the point to send the form. Tell the contractor which checks you did when they call, so they can come prepared. Your first booked job through this site carries $100 off.