Furnace Won't Turn On? 7 Things To Check Before You Call an Oakville HVAC Tech

2026-01-08 · By Mohanad, Owner & Lead Technician, IKAD Mechanical · Troubleshooting

Reviewed: 2026-05-21 · This article is reviewed periodically. Pricing and rebate amounts current as of the date shown.

It's the call we run several times a week in January. Furnace dead. House getting cold. Before you panic, work through this list. About one-third of the no-heat calls we go on turn out to be something the homeowner could have fixed in five minutes.

1. Check Your Thermostat

Sounds dumb. We've seen it. Switch the system to Heat (not Cool, not Off). Raise the setpoint at least 3°C above current room temperature. If it's a smart thermostat (Ecobee, Nest), check it's not in some scheduled or away mode. If the screen is blank, change the batteries.

2. Check the Breaker

Your furnace is on its own breaker (usually 15A) in the main panel. If it tripped, flip it fully Off then back to On. If it trips again immediately, stop, that's a real electrical problem; call us.

3. Check the Switch on the Side of the Furnace

Most furnaces have a literal light-switch on the side of the unit (or near the basement stairs) that controls power. It can get flipped accidentally, sometimes by a cleaner, sometimes by someone changing the filter. Make sure it's On.

4. Check the Filter

A clogged filter can trigger the furnace's high-limit safety, which locks out the heat. Pull the filter, if you can't see light through it, replace it (or run without one for a few hours while you find a new one).

5. Check the Condensate Drain

If you have a high-efficiency (condensing) furnace, look for a small clear plastic line draining into a floor drain or a pump. If the drain is clogged, the safety switch will refuse to let the furnace fire. Disconnect the line, blow it clear, reconnect.

6. Check the Air Pressure / Vent

Step outside and look at the two PVC pipes coming out of the side of your house (the intake and exhaust for the furnace). Are they blocked by snow, ice, or a squirrel's nest? Clear them. Birds and snow drifts are common winter culprits in Oakville.

7. Cycle the Power

Turn the furnace switch Off, wait 60 seconds, turn it back On. Hear the inducer motor start? Good sign. No sound at all after 90 seconds? Call us.

When To Stop and Call

If your furnace is showing an LED error code (visible through a small window on the front), write it down, that tells us exactly what failed. If you smell gas, leave the house and call Enbridge's emergency line (1-866-763-5427) first, then call us. If the furnace is over 18 years old and you're getting frequent no-heat calls, the math has tipped: you're paying for repairs on a system that won't last another winter, and there are real rebates available on a replacement.

Need same-day no-heat service in Halton? Request emergency service or call (905) 491-6943, we're set up to dispatch within hours during winter.

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