Furnace Not Turning On? Check These 8 Things
Updated 2026 — East Hook Heating & Gas Ltd. — TSSA Reg. #FS-R-52587
Before you pay for a service call, run through this list. About one in four no-heat calls turns out to be something a homeowner can safely fix in five minutes. Everything past step eight belongs to a licensed gas technician.
The Safe Homeowner Checklist
- —1. Thermostat — set to HEAT, fan on AUTO, and the setpoint at least 3 degrees above room temperature.
- —2. Thermostat batteries — a dying battery is the single most common false alarm.
- —3. Breaker and service switch — check the panel, then the light-switch-looking disconnect on or beside the furnace. It gets flipped by accident constantly.
- —4. Door panel — the blower door has a safety switch. If the panel isn't fully seated, the furnace will not fire.
- —5. Air filter — a clogged filter overheats the unit and trips the limit switch. Replace it if you can't see light through it.
- —6. Condensate — high-efficiency furnaces make water. A plugged drain or full trap trips the overflow switch and shuts the furnace down.
- —7. Exterior vents — clear snow, ice and nests from the intake and exhaust pipes outside. Critical in Wasaga Beach and Collingwood snow belts.
- —8. Fault code — read the flashing LED through the inspection window and note the pattern before you call.
Stop and Call Immediately If
- —You smell gas — leave the house first, then call the gas emergency line, then call us.
- —Your CO alarm is sounding.
- —You see soot, scorch marks or a yellow, lazy burner flame instead of crisp blue.
- —The furnace has a red tag attached.
- —There is water pooling around the unit or an electrical burning smell.
What We Check That You Can't
Once the basics are ruled out, the fault is usually in the ignition sequence: flame sensor, hot-surface igniter, pressure switch, inducer motor, gas valve or control board. Diagnosing those requires meters, manometers and combustion analysis — and in Ontario, gas work legally requires a TSSA-certified technician.
Frequently Asked Questions
Why is my furnace blowing cold air?
Most often the burners are failing to stay lit — a dirty flame sensor, a failing igniter or a blocked vent. The blower keeps running while no heat is produced. It can also be as simple as the thermostat fan being set to ON instead of AUTO.
What do the flashing lights on my furnace mean?
The LED behind the inspection window flashes a fault code. The legend is printed on the inside of the furnace door — count the flashes and read the code before calling; it speeds up the visit.
Should I keep resetting my furnace?
One reset is reasonable. Repeated resets are not — lockouts exist for a safety reason, and forcing repeated ignition attempts can make the failure worse.
How quickly can you come out for no heat?
We prioritize no-heat calls, especially in a cold snap. Evenings and weekends are available at an overtime rate.