Furnace Troubleshooting Wizard
Diagnose Your Heating Problem Fast

If your furnace isn’t working, our Free troubleshooting wizard asks a few quick questions and tells you the likely cause in under a minute
plus whether it’s safe to fix yourself or time to call an HVAC technician.
🩺 Symptom-Based Diagnosis
🔧 DIY vs Pro Guidance
⚡ Instant Results
🔥
Furnace Troubleshooting Wizard
Which furnace issue are you having? Answer a few quick questions to help identify the most likely cause of your furnace problem and what to do next.
What is the main issue you’re experiencing with your furnace?
What color is your furnace flame?
What sound do you hear from your furnace?
How is the heating performance?
When was your last professional maintenance?
Would you like to receive a free no-obligation estimate from our local contractor partners as well?
Great! Almost done, your result is on the next page.
Please enter your contact details so our Certified contractors can provide estimates as well.
This field is required.
Please enter a valid email address.
Please enter your phone number.
Please enter your city or postal code.

By submitting this form, you are giving your consent to receive phone calls and text messages from our contractor partners.

You’re almost done! Where do we send the results?
Enter your details below to see your diagnosis. Please provide your details to see your results.
Name is required.
Email is required.
City is required.
🔍 Diagnosis Complete

Get a Free Repair Estimate

Connect with certified local HVAC technicians who can diagnose and fix your furnace fast.

Get Free Quotes

Common Furnace Problems & Solutions

Most furnace problems have a handful of common causes. Before calling an HVAC technician, work through the basic checks below many homeowners resolve a furnace not working issue in minutes without a service call
SymptomLikely CauseDIY or Pro?Est. Repair Cost
No heat at allTripped breaker, thermostat, pilot lightDIY first$0 – $350
Furnace won’t stay onDirty flame sensor, thermocouplePro recommended$150 – $300
Short cycling (on/off rapidly)Overheating, dirty filter, blocked flueDIY first$0 – $200
Loud banging noiseDirty burners, duct expansion, cracked HXPro required$200 – $1,500
Blower runs but no heatIgnitor failure, gas supply issuePro required$150 – $450
High gas billsDirty filter, low AFUE, duct leaksDIY first$0 – $500
Yellow or orange flameIncomplete combustion, CO riskPro immediately$200 – $1,200
Error code on displayVaries by code — see wizardWizard + Pro$150 – $800

Step 1: Before You Call a Technician — Check These First

🔌 Check the Power
Ensure the furnace power switch (looks like a light switch near the unit) is ON. Check your electrical panel for a tripped breaker labelled “Furnace” or “HVAC.”
🌡️ Check the Thermostat
Make sure the thermostat is set to HEAT (not Cool or Fan), the temperature is set above room temperature, and the batteries aren’t dead.
🗂️ Replace the Air Filter
🗂️ Replace the Air Filter — A severely clogged air filter is one of the most common causes of furnace shutdowns. Not sure which one to buy? See our furnace filter buying guide.
If you can’t see light through the filter, replace it immediately.
🚪 Check Vents & Registers
Make sure all supply and return air vents in your home are open and unobstructed by furniture, curtains, or debris.
🔥 Check the Pilot Light
For older furnaces with a standing pilot light — check if it’s lit. Instructions for relighting are usually on a label inside the furnace door.
🧊 Check for Frozen Flue
In very cold weather, the exhaust flue pipe can ice over. Inspect the PVC exhaust pipe that exits through your wall or roof for ice blockages.

Furnace Error Codes: What They Mean

Most modern furnaces display error codes via LED flashes or a digital screen when something goes wrong. The number of flashes corresponds to a specific fault code look for the code chart on a sticker inside the furnace door, or use our troubleshooting wizard to decode common error codes for top Canadian furnace brands (Lennox, Carrier, York, Goodman, Keeprite, Napoleon).

When to Call a Technician Immediately

Some furnace issues require immediate professional attention for safety reasons see all warning signs you need emergency furnace repair. Call an HVAC technician or emergency line right away if you notice: a yellow or orange flame (CO risk), the smell of natural gas (evacuate and call your gas utility see Enbridge Gas’s appliance safety guidance), a cracked or corroded heat exchanger, or your carbon monoxide detector is alarming. see TSSA’s carbon monoxide safety resources.

💡 Maintenance Saves Repair Bills

Annual professional tune-ups ($100–$200) prevent 80% of common furnace breakdownsor check 7 things to check when your furnace stops working first. see Natural Resources Canada’s heating system maintenance guide for a full seasonal checklist.
Replace filters every 1–3 months during heating season — it takes 2 minutes
Keep the area around your furnace clear of combustibles and obstructions
Test your carbon monoxide detectors monthly — furnaces produce CO when combustion is incomplete

Common Questions Answered Of Furnace Troubleshooting Wizard

Why does my furnace turn on but blow cold air?

Cold air usually means the fan is set to ON instead of AUTO, the igniter or gas valve is failing, or — if it keeps happening you may be seeing early signs your furnace needs replacement.

A single bang at startup usually means delayed ignition from dirty burners; banging during operation can signal duct expansion or a cracked heat exchanger use our repair vs. replace guide to decide your next step.

Canadian HVAC pros recommend one professional furnace tune-up per year, ideally every September or October before heating season starts.

A standard tune-up covers burner and heat exchanger cleaning, gas pressure and safety-control checks, and CO testing see typical furnace tune-up and repair costs for pricing.

Rebates Available
Ontario homeowners may qualify for energy-efficiency rebates through the Home Renovation Savings program, plus manufacturer and municipal incentives on qualifying systems
$5,000
Eligibility and amounts vary by upgrade.
Get a Free Quote

Connect with trusted local HVAC contractors in your area. Get 3 free quotes — no obligation.