If your furnace is not working, start with the simple checks: the thermostat, the breaker, the furnace power switch, the filter and the vents. Many no-heat problems turn out to be one of these, and most take a few minutes to check.
Below are 9 safe checks, what to leave to a technician, and the signs that mean you should call right away. If you smell gas or your carbon monoxide alarm goes off, go straight to the safety section.
Article summary
- Most furnace calls start with something simple: the thermostat, a tripped breaker, the furnace power switch, a clogged filter or a blocked vent.
- Check those 9 things first. They take a few minutes and need no tools beyond a flashlight.
- Don’t open the burner area, touch gas valves, clean the flame sensor or keep pressing reset. Those are jobs for a licensed technician.
- If you smell gas or your carbon monoxide alarm goes off, get everyone outside and call FortisBC at 1-800-663-9911 or 911.
- Still no heat after the checks? Call Mendieta ACS at (604) 802-1109. We’re open 24/7.
Safety first: when to stop and get out
If you smell gas (a rotten egg smell), FortisBC’s advice is to stop what you’re doing, go outside first, then call the FortisBC Emergency Line at 1-800-663-9911 (24 hours) or dial 911.
If your carbon monoxide (CO) alarm goes off, or people feel headaches, nausea or drowsiness that ease outside, FortisBC says to turn off your appliances, get everyone (pets too) out of the building, call 911 or 1-800-663-9911, and get medical help for any symptoms. You can’t see or smell CO.
Once it’s declared safe, have a licensed technician find the cause before you use the furnace again.
9 things to check when your furnace is not working
Work through these in order. Each one is safe for a homeowner and needs nothing more than a flashlight.
1. The thermostat setting
Make sure the thermostat is set to Heat (not Cool or Off) and set a few degrees above the room temperature. Check the schedule too: a program may have switched it to a lower "away" temperature.
2. The thermostat batteries
Many thermostats run on batteries. If the screen is blank or faded, replace the batteries and try again. Dead batteries are a simple reason a furnace won’t turn on.
3. The fan setting (if your furnace is blowing cold air)
If the fan is set to On, the blower runs all the time, even when the furnace isn’t heating. That feels like the furnace is blowing cold air between heating cycles. Set the fan to Auto so it only runs when there’s heat to move.
4. The breaker and the furnace power switch
A gas furnace still needs power. Check your electrical panel for a tripped furnace breaker, then the furnace power switch, which usually looks like a light switch on or near the furnace. If the breaker trips again after a reset, leave it off and call a technician.
5. The furnace door
Most furnaces have a safety switch that stops them from running if the front panel isn’t closed properly. If someone changed the filter recently, make sure the door is seated firmly. Never tape or hold down this switch to force the furnace to run.
Related service: Furnace repair in the Lower Mainland
Mendieta ACS installs gas, electric and oil furnaces and handles furnace troubleshooting and repairs, including thermostat issues, gas valve and pilot light repairs and performance problems. See our furnace installation and repair services.
6. The air filter
A clogged filter chokes the airflow. The furnace can overheat and shut itself off, which shows up as weak heat or a furnace that keeps shutting off. Hold the filter up to a light. If you can’t see through it, replace it with the same size (printed on the frame).
7. The vents and return grilles
Make sure supply vents are open and return grilles (the larger grilles that pull air back to the furnace) aren’t blocked by furniture, rugs or boxes. Closing too many vents makes the furnace work harder.
8. The outside vent pipes
High-efficiency furnaces usually have two plastic pipes through an outside wall or the roof. Snow, ice, leaves or a nest can block them and shut the furnace down. Clear what you can reach safely. Don’t climb onto a wet or icy roof.
9. The condensate drain
High-efficiency furnaces make water as they run, which drains through a small tube and sometimes a pump. If the drain clogs or the pump fails, a safety switch can stop the furnace. Look for water around the furnace. Ongoing leaks need a technician.
What not to do yourself
Some fixes you’ll see online are jobs for a licensed technician. For your safety, don’t:
- Open the burner area or remove panels beyond the filter door.
- Turn, loosen or adjust gas valves or gas lines.
- Clean or sand the flame sensor. It means working inside the burner area.
- Keep pressing the reset button. Repeated lockouts mean something is wrong.
- Bypass or tape over any safety switch.
- Heat the house with the oven or with a barbecue or camping heater indoors. These can produce carbon monoxide.
Furnace pilot light out or furnace not igniting
Many newer furnaces use electronic ignition instead of a pilot light that stays lit. If the furnace tries to start, clicks, then stops, the furnace is not igniting. Turning the power switch off and on once can reset it. If it locks out again, call a technician.
If an older furnace has its furnace pilot light out, read the lighting instructions on the label inside the door. Only follow them if they’re clear and there is no gas smell. If the pilot won’t light or stay lit, stop and call a technician.
Furnace keeps shutting off or short cycling
Furnace short cycling means the furnace runs briefly, shuts off, then starts again over and over. It’s uncomfortable and adds wear.
Start with checks 1, 6, 7 and 8: thermostat, filter, vents and outside pipes. If that doesn’t fix it, the cause may be a dirty flame sensor, an overheating limit switch, a badly placed thermostat or an oversized furnace. A technician can test these safely.
No heat after the 9 checks? We’re open 24/7.
Call Mendieta ACS at (604) 802-1109 or request a free quote online. Learn more about our furnace repair services.
Furnace smells like burning
A light dusty smell when the heat first comes on in the fall is common. It’s dust burning off and usually fades after a few cycles.
When a furnace smells like burning in a different way, take it seriously:
- A strong electrical or burning plastic smell: turn the furnace off at the thermostat and call for repair. It can point to an overheating motor or wiring.
- Smoke from the furnace or vents: turn the furnace off, leave the house if needed, and call 911.
- A rotten egg smell: this is a possible gas leak. Leave the house and call FortisBC at 1-800-663-9911 or 911 from outside.
When to call for emergency furnace repair right away
Call a technician without waiting if:
| Sign | What it can mean | What to do |
|---|---|---|
| No heat after all 9 checks | A failed part, ignition or control problem | Call for repair |
| Breaker trips again after a reset | An electrical fault | Leave it off, call for repair |
| Furnace locks out after one reset | A safety control is stopping it | Don’t keep resetting, call for repair |
| Loud banging, grinding or squealing | A mechanical problem inside the furnace | Turn it off, call for repair |
| Water keeps pooling around the furnace | A drain, pump or other leak | Call for repair |
| Strong burning or electrical smell | Overheating motor or wiring | Turn it off, call for repair |
| Gas smell or CO alarm | A possible gas leak or CO | Get out, call FortisBC 1-800-663-9911 or 911 |
In a cold snap, don’t wait if babies, older adults or anyone with health concerns live in the home.
Repair, replace or prevent the next breakdown
If your furnace is older, keeps breaking down or no longer heats the home properly, replacing it may make more sense than another repair. We can inspect it and explain your options, including furnace and dual fuel rebates and financing. Regular servicing through our maintenance plans helps catch worn parts before they fail mid-winter.
Get your heat back on
When your furnace is not working, do the 9 safe checks first. Leave burners, gas valves, the flame sensor and safety switches to a professional. If you smell gas or your CO alarm sounds, get out and call FortisBC or 911.
If the heat still isn’t on, Mendieta ACS is here 24/7 for emergency furnace repair in Coquitlam, Port Coquitlam, Burnaby and across the Lower Mainland. Call us at (604) 802-1109 or get a free quote online.
Frequently asked questions
Why is my furnace blowing cold air?
Check the thermostat first. If the fan is set to On instead of Auto, the blower runs even when the furnace isn’t heating. A dirty filter, a blocked outside vent pipe or an ignition problem can also cause it.
Why won’t my furnace turn on?
Usually something simple: the thermostat is off or its batteries are dead, a breaker tripped, the furnace power switch is off, or the furnace door isn’t closed properly. If all of those are fine, it needs a professional diagnosis.
Why does my furnace keep shutting off?
This is called short cycling. A clogged filter, closed vents, a thermostat problem or a blocked outside vent pipe can cause it. If it keeps happening after those checks, call a technician.
Is a burning smell from my furnace normal?
A light dusty smell when the heat first comes on in the fall usually fades. A strong electrical or plastic smell, or smoke, is not normal: turn the furnace off and call for repair. A rotten egg smell means leave the house and call FortisBC or 911.
Does Mendieta ACS do emergency furnace repair?
Yes. Mendieta ACS is open 24/7 and repairs furnaces across Coquitlam, the Tri-Cities, Burnaby, Vancouver, Surrey and the Lower Mainland. Call (604) 802-1109.
