Why won't my furnace ignite?

A furnace that won't ignite is typically caused by issues with the gas supply, ignition system, or safety controls that prevent the unit from starting safely. This is a situation that requires immediate professional attention since it involves gas appliances and potential safety hazards.

The most common causes include a faulty igniter or pilot light, gas supply problems, or blocked venting. Modern furnaces use either a hot surface igniter or electronic ignition system that can fail over time. If your furnace is trying to start but you hear clicking without ignition, the igniter may be cracked or worn out. Older furnaces with pilot lights may have the pilot extinguished due to drafts, thermocouple issues, or gas supply interruptions.

Safety controls are designed to prevent dangerous situations and will stop ignition if they detect problems. A dirty flame sensor, blocked air intake, or restricted exhaust vent can trigger these safety shutoffs. The furnace's control board monitors these systems and won't allow ignition if conditions aren't safe. Additionally, issues with the gas valve, pressure switch, or limit switches can prevent the ignition sequence from completing.

In Ottawa's climate, furnace reliability is critical during winter months. Never attempt to bypass safety controls or work on gas components yourself - this work requires a TSSA-licensed G2 technician. If you smell gas at any time, leave your home immediately and call Enbridge at 1-866-763-5427.

Check your thermostat settings and replace your air filter first, as these simple issues can sometimes prevent ignition. If the problem persists, turn off your furnace and contact a licensed HVAC professional immediately. Ottawa HVAC Pro provides emergency furnace repair services and can safely diagnose and resolve ignition problems to restore heat to your home.