Every first cold week of the season, our phones fill with the same call: "the furnace won't come on at all." Work through this list in order — it runs from free ten-minute checks to the things that genuinely need a technician.
The 7 checks, in order
Thermostat isn't actually calling for heat
✓ You can fix thisSet to HEAT (not COOL or OFF), setpoint above room temperature, and fresh batteries. A blank or frozen display is a thermostat problem, not a furnace problem.
Raise the setpoint 5 degrees above room temp and wait 5 minutes — many systems have a built-in start delay.
The furnace's power switch is off
✓ You can fix thisThere's a switch on or beside the furnace that looks exactly like a light switch. It gets flipped by kids, painters, and anyone reaching for a basement light — this is genuinely one of our most common "repairs."
Flip it up and give the furnace a few minutes. While you're there, check the breaker panel for a tripped "furnace" or "air handler" breaker — reset it once, and if it re-trips, stop and call.
Clogged filter tripped the overheat lockout
✓ You can fix thisA starved furnace overheats and its limit switch shuts it down for safety. After several lockouts, many furnaces stop retrying altogether.
Replace the filter, then cut power to the furnace for 60 seconds (wall switch or breaker) to clear the lockout and let it restart fresh.
Pilot light or ignition failure
DIY only on older pilot modelsOlder furnaces have a standing pilot that can blow out; newer ones use electronic ignitors that wear out and crack. Ignition is the most common true mechanical failure on no-start calls.
Relighting a standing pilot per the printed instructions on the unit is fine. If the pilot won't stay lit, or your furnace uses electronic ignition and clicks without firing, that's a service call — usually a quick, inexpensive one.
Condensate safety switch (high-efficiency models)
✓ Worth checkingHigh-efficiency furnaces produce water. If the condensate pump fails or the drain clogs, a float switch cuts the furnace off to prevent a flood.
Look for a small pump or trap near the furnace base. If its reservoir is full of water, the pump or drain is the problem — empty it and it may restart, but the clog needs fixing or it'll trip again.
No gas supply
✓ Quick checkA closed valve on the gas line (handle should be parallel to the pipe), a utility interruption, or an empty propane tank all present as a furnace that cranks but never fires.
Check whether your stove or other gas appliances work. If nothing in the house has gas, call your utility — not us.
Blower motor or control board failure
Call a proIf you've cleared everything above and the furnace is silent — no click, no hum, no fan — the blower motor, capacitor, or control board is the likely culprit, especially on units 12–15+ years old.
On an older furnace this is the repair-or-replace decision point. Ask for both quotes; we provide both on every visit, with financing options if replacement makes more sense.
Stop doing this every winter
Almost everything on this list — ignition wear, clogged filters, condensate clogs, weak capacitors — gets caught in a fall heating tune-up before the first cold night. Our membership plan includes it every year automatically, with priority scheduling when the season gets busy.
Still no heat?
Same-day heating repair across South Jersey, Mon–Fri, plus emergency weekend service. Family-owned, 4.8★ on Google.
Serving Camden, Gloucester, Burlington, Atlantic, Cape May, Cumberland, and Salem counties from Runnemede, NJ — see all service areas, explore our heating services, or browse more homeowner guides.