No Heat in Your Long Island Home? What to Check First

First checksFurnaceBoilerWhen to stopFAQ

When the heat quits on a cold night, a few checks are safe for any homeowner and fix a surprising share of calls. Anything involving gas, fuel lines, wiring inside the unit or a boiler’s water feed is a job for a technician.

Five Checks for Any System

1. Thermostat – set to Heat and a few degrees above room temperature. Replace the batteries if the screen is blank or dim.
2. Power switch – furnaces and boilers have a light-switch-style emergency switch at the top of the basement stairs or on the unit. It’s easy to flip off by mistake.
3. Breaker – look for a tripped breaker labeled furnace, boiler or burner. Reset it once; if it trips again, leave it off and call.
4. Fuel – on oil, check the tank gauge. On gas, check that a stove burner lights. An empty oil tank is one of the most common first-cold-night calls.
5. Reset button – oil burners have a red reset button on the control box. Press it once only. Pressing it again and again floods the chamber with oil and can cause a puff-back.

If You Have a Furnace (Forced Air)

• Filter – a clogged filter makes the furnace overheat and shut itself off. Replace it if you can’t see light through it.
• Blinking light – most gas furnaces have a status light behind a small window in the lower panel. Count the blinks and match them to the code chart on the panel door.
• Condensate line – high-efficiency furnaces drain water through a plastic line. A clogged line or full pump trips a safety switch and the furnace stops.
• Registers – make sure supply registers are open and nothing blocks the return grille.

Don’t remove burner covers or bypass any switch. A furnace that starts, runs a few minutes and shuts off usually has a dirty flame sensor or a pressure switch problem, which is a short repair. See furnace repair for the common causes.

If You Have a Boiler (Steam or Hot Water)

• Steam: sight glass – the glass tube on the side of the boiler should be about half full. If it’s empty, turn the boiler off and let it cool before adding water. Cold water in a hot, dry boiler can crack it.
• Hot water: pressure gauge – most home systems run around 12 to 20 psi. Close to zero means the system needs water or has a leak.
• Some rooms cold, others fine – on hot water that’s usually air in the lines or a stuck zone valve. On steam it’s often a clogged radiator vent.
• Circulator – on hot water systems you can usually hear or feel the pump running while the boiler fires. Silence with a hot boiler points to the pump or its relay.

Our guide to steam boiler problems covers banging pipes, cold radiators and short cycling in more detail.

When to Stop and Call

• You smell gas. Leave the house, don’t flip switches, and call National Grid or 911 from outside.
• A carbon monoxide alarm goes off, or anyone has headaches or nausea that ease when they step outside.
• You see soot or smell oil or smoke around an oil burner.
• The breaker or the reset button trips a second time.
• Water is pooling around the boiler, or its pressure keeps climbing toward 30 psi.

While you wait, open cabinet doors under sinks on outside walls and let a faucet drip so pipes don’t freeze.

What a No-Heat Visit Usually Costs

A diagnostic visit on Long Island typically runs $100–$200, and after-hours calls cost more. Common fixes such as a flame sensor, igniter, or an oil burner nozzle and filter are usually a few hundred dollars. You approve the price before any repair starts.

No-Heat FAQ