Losing heat is stressful, but most of what happens in the first few minutes decides whether it’s a quick fix or a real repair.
Step 1: Check the Basics First
Before calling anyone, check these three things — they solve a surprising number of “no heat” calls on their own:
- Thermostat — is it set to Heat, and is the target temperature above the current room reading? Check batteries if it’s battery-powered.
- Breaker panel — has a breaker tripped for the furnace circuit? In newer Markham homes, check whether your HRV/ERV shares a breaker with the furnace.
- Furnace switch — many furnaces have a wall switch near the unit that looks like an ordinary light switch. Easy to bump off in a mechanical room.
Step 2: Check the Filter
A severely clogged filter can cause a furnace to overheat and shut itself down as a safety measure. If it’s visibly caked with dust, replace it and see if the furnace restarts after a few minutes.
Step 3: Don’t Confuse an HRV/ERV Issue With a Furnace Issue
If your home feels cold but the furnace itself seems to be running, and you’re also noticing stuffy air or condensation, the issue might involve your ventilation system rather than the furnace directly. They’re separate pieces of equipment, and troubleshooting one as if it were the other wastes time.
Step 4: Look for an Error Code
Most modern furnaces have a small window showing a blinking light code. Photograph the pattern before you call — it tells a technician exactly what fault the furnace is reporting, which speeds up the repair.
What Not to Do
Don’t take apart the furnace cabinet, don’t reset the system repeatedly hoping it “catches,” and don’t attempt any gas line or ignition work yourself. Gas components should only be handled by a TSSA-licensed technician.
When to Call
If the basics check out and the furnace still won’t run — or you smell gas at any point — stop troubleshooting and call immediately. A York Region winter isn’t something to sit on overnight, especially with young kids, elderly family members, or pets in the house.
Our dispatcher is available 24/7, and a technician can typically be on-site within 60 minutes.