Furnace
Furnace Repair in Ontario
How Furnaces Fail
Modern gas furnaces fire through a strict sequence: the inducer motor proves airflow, the igniter heats or sparks, the flame sensor confirms combustion, and only then does the blower push warm air through your ducts. If any single step fails, the control board stops the sequence, often flashing an error code that points toward the cause rather than leaving a technician guessing.
The most common repair calls we get are a dirty flame sensor causing repeated shutdowns, a cracked igniter that no longer glows hot enough, or a tripped pressure switch from a blocked condensate line on high efficiency models. Older mid efficiency furnaces fail differently than newer condensing units, so knowing which type you have changes where we start testing and what parts are likely involved.
Service Inclusions
- ✓ Igniter & flame sensor
- ✓ Blower & inducer motors
- ✓ Control boards
- ✓ Heat exchanger inspection
Typical price range
$200 to $900
Typical Ontario price range before tax. Your actual price depends on your equipment, parts and access, and is confirmed after we assess the job.
Get a tailored estimate →Signs You Need Repair
Furnace blows cold or won't start
A dirty flame sensor, failed igniter or tripped pressure switch from a blocked condensate line are the most common culprits behind no heat calls.
Short cycling on and off
The furnace starts, runs briefly and shuts down repeatedly, often from overheating, a clogged filter or a control board sensing a fault.
Loud bangs, squeals or rattling
Delayed ignition causing a bang, a worn blower bearing squealing, or a loose panel rattling all point to issues that worsen if left alone.
Flashing error code on the control panel
Most furnaces log a blink pattern tied to a specific fault, which tells us where to start testing instead of opening the cabinet blind.
Our Repair Process
- 01
We check the control board's diagnostic light pattern
And ask what you've noticed, narrowing down the likely fault before opening any panels.
- 02
Igniter resistance
Igniter resistance, flame sensor microamp readings, pressure switches and inducer motor function are tested in the order the furnace actually fires.
- 03
Once the fault is confirmed
We replace the specific component, whether that's an igniter, sensor, board or motor, rather than swapping multiple parts speculatively.
- 04
The furnace is cycled through startup
Run and shutdown at least once to confirm the repair holds and temperatures rise normally at the registers.
Carbon Monoxide Safety
A cracked heat exchanger can leak carbon monoxide into the air your furnace circulates through the house, so every repair visit includes a visual check of accessible heat exchanger surfaces and a carbon monoxide test near the registers. If you ever hear your CO detector alarm, leave the house immediately and call 911 or your gas utility from outside; don't attempt to diagnose the furnace yourself first. We also verify combustion venting is clear and properly connected before considering any repair finished.
What Repairs Typically Involve
Flame sensor or igniter replacement
Among the most common and least expensive furnace repairs, usually resolved in a single visit once confirmed by testing.
Blower motor or inducer motor repair
More involved since these are larger mechanical parts, with cost depending on whether the motor can be rebuilt or needs full replacement.
Control board replacement
Typically the most expensive single part repair, reserved for confirmed board failures rather than unexplained fault codes.
Diagnosing the actual failed part instead of replacing several components on suspicion keeps repair costs tied to what's really wrong. It also means the furnace is more likely to run reliably afterward, since parts that weren't the problem are left alone to keep working.
Homeowner Tips
A clogged filter restricts airflow enough to trip
Safety switches and mimic a real mechanical fault, so checking it first can save an unnecessary call.
Most control boards have a small light that blinks
A pattern; counting the blinks before we arrive speeds up diagnosis.
If it shuts off and you keep flipping the switch back
On, you can mask a safety lockout that's trying to protect the system from a real fault.
Choosing the Right Repair Team
We repair furnaces from mid efficiency units through current condensing models, testing the full ignition sequence rather than guessing at the first part that looks worn.
Sequence based diagnosis
We test components in the order the furnace actually fires, which finds the real fault faster than random part checks.
Experience across furnace ages
Older standard efficiency units fail differently than newer condensing models, and we know what to check on each.
Heat exchanger checks included
Every repair call includes a visual and carbon monoxide check, not just a fix for the symptom you called about.
Repair FAQs
+Why does my furnace blow cold air before shutting off?
This is often a dirty flame sensor that can't detect the flame reliably, so the control board shuts the gas off as a safety measure partway through the cycle.
+What does a flashing light on my furnace mean?
Most control boards use a blink pattern to indicate a specific fault code. Counting the blinks and checking your furnace's manual or calling us helps identify the issue before a visit.
+Is it worth repairing an older furnace?
The furnace's age, repair cost and how often it's been failing all factor into the decision. A single repair on a ten year old unit is often worthwhile; repeated repairs may point toward replacement instead.
+How quickly can a furnace repair happen?
Common repairs like a flame sensor or igniter are often same visit fixes once diagnosed. Parts that need to be sourced, like certain control boards, can take longer.
+Can a dirty filter really stop my furnace from running?
Yes. A severely clogged filter restricts airflow enough to overheat the furnace and trip a safety switch, shutting the system down well before any other component fails.
+What should I do if my carbon monoxide alarm goes off?
Leave the house immediately and call 911 or your gas utility from outside. Don't try to turn off the furnace or investigate the cause yourself before getting everyone out safely.
Areas We Serve
HeatNest repairs furnaces across Ontario, working on both mid efficiency and high efficiency condensing units in homes dealing with no heat calls and ongoing noise or cycling issues.
Acton · Adjala Tosorontio · Ailsa Craig · Ajax · Angus · Arva · Aurora · Aylmer · Ayr · Barrie · Bolton · Bowmanville · Bradford · Brampton · Brantford · Brooklin · Burford · Burlington · Caledon · Cambridge · Clarington · Collingwood · Courtice · Delaware · Dorchester · Dutton · East Gwillimbury · East York · Enniskillen · Erin · Etobicoke · Exeter · Fort Erie · Georgetown · Georgina · Glencoe · Grimsby · Guelph · Halton Hills · Hamilton · Hensall · Ilderton · Ingersoll · Innisfil · Keswick · Kilworth · King City · Kitchener · Komoka · Lincoln · London · Lucan · Markham · Midland · Milton · Mississauga · Mitchell · Mitchell Corners · Mono · Mount Brydges · New Tecumseth · Newcastle · Newmarket · Niagara Falls · Niagara on the Lake · Nobleton · North York · Norwich · Oakville · Orangeville · Orillia · Oro Medonte · Orono · Oshawa · Ottawa · Parkhill · Pelham · Pickering · Port Colborne · Port Stanley · Puslinch · Richmond Hill · Scarborough · Schomberg · Scugog · Shedden · Smithville · Springwater · St. Catharines · St. Marys · St. Thomas · Stratford · Strathroy · Sutton · Thamesford · Thorndale · Thornhill · Thorold · Tillsonburg · Toronto · Tottenham · Tyrone · Unionville · Uxbridge · Vaughan · Wasaga Beach · Waterloo · Welland · Whitby · Whitchurch Stouffville · Woodstock
What customers say about our furnace repair
"The technician showed up on time, explained exactly what was wrong and had everything working the same afternoon. No upselling, just honest work."
"Very knowledgeable and patient with my questions. I finally understand how my system works and what to watch for."
"They walked me through repair versus replacement options without pressure. I'll be calling HeatNest again."
Get It Fixed
No heat is never convenient. Call HeatNest at (289) 801-7262 to get your furnace diagnosed and repaired properly, not just patched for now.