A furnace that has stopped in a Toronto winter is an emergency when the outdoor temperature is below freezing, when a carbon monoxide alarm has sounded, or when you can smell gas — those three call for a technician now, not in the morning. Everything else can usually wait for business hours without risk. Our line answers 24/7, and we do not add overtime, weekend or holiday surcharges to the bill.
What counts as a furnace emergency overnight
- A carbon monoxide alarm sounding — get everyone outside first, then call 911 or the fire service, and only afterward call an HVAC contractor
- The smell of gas anywhere in the house — leave, touch no switches, and call Enbridge Gas from outside; the sequence is in our guide on what to do if you smell gas
- No heat with outdoor temperatures below freezing, particularly overnight when the house keeps losing heat and nobody is awake to watch the pipes
- No heat in a house with an infant, an elderly resident, or anyone whose health depends on a stable indoor temperature
- Water pouring from the furnace or the humidifier onto a finished floor
- Burning, electrical or hot-metal smells that do not clear within a few minutes of the first fire-up of the season
A furnace that is short-cycling, noisy, or heating unevenly is a service call rather than an emergency. So is a thermostat that has lost its schedule. Booking those during business hours costs less almost everywhere and gets you a longer, more careful visit.
Seven checks to run before you call
- Thermostat: set to Heat, setpoint several degrees above the room, and fresh batteries in it if it is battery-powered
- Furnace switch: the light-switch-looking one on or beside the furnace, which gets flipped off by anyone moving boxes in the basement
- Breaker: the furnace circuit at the panel, plus the disconnect if there is one
- Filter: pull it and hold it to a light — a filter that is packed solid will trip the limit and shut the burner down
- Gas: check that other gas appliances still work; if the stove will not light either, the problem is the supply, not the furnace
- Furnace door: the blower door has a safety switch and the furnace will not run with it off its catch
- Vent terminations outside: on a condensing furnace, snow or ice over the PVC pipes will lock the unit out on a pressure switch fault
Those seven resolve a real share of the no-heat calls we take, and none of them requires tools. If the furnace runs after one of them, book a service visit anyway — a filter packed solid or a snow-blocked vent has usually been stressing the unit for weeks.
Why the furnace locked out, and the one reset worth trying
Gas furnaces count their failed ignition attempts. After about three tries the control board stops trying and goes into hard lockout, which is a safety feature rather than a fault in itself. Cutting power at the furnace switch for 30 seconds and restoring it clears the lockout and lets the sequence run once more.
Try that once. If it lights and stays lit, watch it through a full cycle. If it locks out again, stop — repeated resets on a furnace that will not prove flame put unburned gas through the heat exchanger, and the underlying fault is almost always a dirty flame sensor, a failed igniter, a blocked condensate trap or a pressure switch that is not making. Read the flash code on the control board through the sight glass and have it ready when you call.
What emergency furnace repair costs after hours in the GTA
Free quotes, written pricing.
- Standard business-hours diagnostic across the GTA: roughly $80–$150, usually credited toward the repair
- Typical after-hours dispatch fee at most GTA companies: $150–$300, and some add a percentage to the labour on top
- Common overnight fixes — flame sensor, igniter, capacitor: $150–$450
- Larger parts — blower motor or control board: $500–$1,500 depending on the motor type and the board
- Most furnace repairs overall: $150–$800, part and labour together
- ZK Mechanical: no overtime, weekend or holiday surcharge, so a 2 a.m. call is billed the same as a Tuesday afternoon
The pattern to watch on any emergency quote is the diagnostic fee disappearing into a large flat number with no breakdown. Ask what the part costs, what the labour costs, and whether the service call is credited. Written pricing before the work starts is a reasonable thing to expect at any hour — more on that in what counts as an HVAC emergency.
Protecting the house while you wait for heat
The risk in an unheated GTA house is not discomfort, it is plumbing. Pipes running through exterior walls, in a cantilevered bay, or along an uninsulated garage ceiling freeze first, and a split copper line does far more damage than the furnace repair ever costs.
- Open the cabinet doors under kitchen and bathroom sinks on outside walls so room air reaches the pipes
- Run a pencil-thin trickle from the tap furthest from the shut-off valve
- Close off unused rooms and keep everyone in one space, ideally one with a working gas fireplace
- Leave the thermostat calling for heat so the furnace fires the moment it is fixed
- If the house will be empty for more than a night, shut the water off at the main and drain the lines
- Do not heat the house with a gas range, a barbecue or an unvented heater — that is how carbon monoxide incidents start
Ontario's Hawkins-Gignac Act requires a working carbon monoxide alarm adjacent to the sleeping areas of any home with a fuel-burning appliance or an attached garage. Test yours before winter, and read how a furnace can leak carbon monoxide so you know which symptoms belong to the house rather than a cold.
How to stop needing the emergency call next winter
Nearly every overnight no-heat call we run has a fall inspection that would have caught it. A flame sensor coated in oxide, a condensate trap half full of sludge, an inducer bearing starting to whine and a filter nobody has changed since spring are all visible in a tune-up and invisible from the top of the basement stairs.
Book that visit in September or early October, before the first cold snap sends the whole city's furnaces into their first hard run of the season. A scheduled visit also gets you a technician with time to look properly rather than one working through a queue.
ZK Mechanical runs 24/7 emergency HVAC service across the GTA and Hamilton with TSSA-licensed technicians, stocked trucks and written pricing at every hour. If you are without heat right now, call the line on this page; if you are reading this in advance, our Toronto furnace repair page covers what we handle locally, and you can book a fall inspection before the queue forms.
Frequently asked questions
Should I turn my furnace off if it keeps shutting down?
If it is cycling on and off but still producing heat, leave it running and book a service call. Turn it off at the furnace switch and stop resetting it if you smell gas or burning, if a carbon monoxide alarm has gone off, if water is pooling under it, or if it locks out again immediately after a reset. Repeated resets on a unit that cannot prove flame are the pattern worth avoiding.
Does emergency furnace repair cost more at night in the GTA?
At most companies, yes. The usual structure is an after-hours dispatch fee of $150–$300 instead of the $80–$150 business-hours diagnostic, sometimes with a premium on the labour rate as well. ZK Mechanical does not add overtime, weekend or holiday surcharges, so the hour you call does not change the price of the work.
How cold does a house get overnight without heat?
It depends far more on the building than the weather — a 1950s bungalow with original windows loses heat several times faster than a 2010s build with a sealed envelope. What matters is not the room temperature but where the plumbing runs. Pipes in exterior walls, cantilevers and uninsulated garage ceilings are at risk long before the living space becomes genuinely unsafe.
Can I use space heaters until the furnace is fixed?
Electric space heaters are fine in moderation: one per circuit, plugged directly into the wall rather than a power bar, and never left running in an empty room or overnight beside bedding. What is never safe is heating with a gas range, an oven, a barbecue or any unvented fuel-burning heater indoors, because those put combustion products into the room you are sitting in.
What information should I have ready when I call?
The furnace brand and model from the rating plate inside the door, the flash code the control board is blinking through the sight glass, whether the blower runs at all, what you have already tried, and whether the outdoor vent pipes are clear. Those four details often tell us which part to bring, which is the difference between one visit and two.