No heat in winter: the homeowner's sequence when the furnace stops

Thermostat first: is it set to Heat with the set point above room temperature, and does it show a call (a flame or heat icon)? Replace dead batteries. Then power: the furnace has a light-switch-style disconnect on or near the cabinet, and a breaker in the panel; both should be on. A furnace with a condensate pump can also stop if the pump's safety switch tripped because the pump is full.

Blower door: the door switch cuts power when the blower compartment door is not fully seated; reseat it, never tape it. Gas: confirm the shut-off valve at the furnace is fully open in line with the pipe — someone may have closed it in the summer. Filter: a loaded filter can trip the limit and make the furnace appear dead; note its condition.

Modern furnaces show a status code on a display or as LED flashes through a window in the door. Write down the exact digits, including any minor digit (for example 33.2), then look the code up on this site's error-code pages for your brand and family. The code identifies the check the furnace failed; it does not name a failed part, and the page will say what a technician tests.

Codes are only meaningful for your furnace's controller, which is why the model number from the rating plate matters: this site documents codes per generation, and the same number can mean different things on different controls.

If the furnace will not restart, set the thermostat to Off so the blower does not run cold air all night, close the doors to rooms you are not using, and protect pipes in unheated areas: let taps drip where freezing is a risk. Do not use the oven or a portable combustion heater as a furnace substitute without checking its own safety and ventilation rules.

If you have a working fireplace or approved space heater, use it with the manufacturer's clearances and ventilation. Never run a generator indoors, and never leave any combustion appliance running unattended while you sleep.

Gas smell and carbon-monoxide alarms are handled before any furnace call: leave the building, call FortisBC at 1-800-663-9911 (gas) or 911 (CO or medical symptoms) from outside, and do not re-enter until told it is safe. BC Wide's own emergency service page says the same thing: no-heat is a priority call, but gas and CO are utility and emergency-service calls.

Call BC Wide with the brand, the full model number from the rating plate, the code exactly as displayed, and whether the furnace still runs at all. That information decides whether the call is priority no-heat service and lets the technician arrive with the right parts and manuals.