Furnace Repair in London, ON: 5 Critical Warning Signs You Can't Ignore This Winter

For optimal performance and safety, it's recommended to have your furnace professionally inspected and serviced once a year, ideally in the fall before the heating season begins (September or October). Annual inspections catch warning signs early, maintain efficiency, prevent breakdowns, and protect your warranty. We offer maintenance plans starting at $149/year that include comprehensive inspections.

Repair costs vary widely depending on the issue: flame sensor cleaning ($90-$150); ignitor replacement ($250-$400); blower motor repair ($400-$800); gas valve replacement ($300-$600); inducer motor replacement ($400-$700); heat exchanger replacement ($1,500-$3,000 — usually leads to furnace replacement). Our diagnostic fee is $175, waived if you proceed with the repair. We provide upfront pricing before any work begins.

While basic tasks like changing the air filter are safe for homeowners, most furnace repairs require specialized knowledge and TSSA certification. For your safety, and to avoid causing further damage or voiding warranties, it is highly recommended to hire a certified HVAC professional. DIY repairs on gas or electrical components are dangerous and can lead to carbon monoxide leaks, fires, or explosions.

A loud banging noise (often called furnace kettling or detonation) usually indicates delayed ignition. Gas builds up in the combustion chamber before igniting, causing a small explosion. This is dangerous and can damage your heat exchanger, leading to carbon monoxide leaks. Turn off your furnace immediately and call a TSSA-certified technician for emergency service. Do not ignore this sound.

Cold air or inadequate heating can be caused by: a clogged air filter restricting airflow; thermostat issues; a faulty flame sensor (furnace lights then shuts off); a failed ignitor; gas supply problems; or a blower motor issue. Check your filter and thermostat first. If those don't resolve the issue, call a professional. Don't wait — during winter, this can lead to frozen pipes.

Short cycling (furnace runs for 2-5 minutes, shuts off, then restarts repeatedly) can be caused by: a dirty flame sensor; an oversized furnace; a clogged air filter; thermostat issues; or a faulty heat exchanger. Short cycling wastes energy, wears out components faster, and prevents proper heating. If your furnace is short cycling, call for professional diagnosis immediately before the problem worsens.

A furnace pilot light should be a strong, steady blue. A yellow or flickering flame is a serious safety concern, as it can indicate incomplete combustion and excess carbon monoxide production. Turn off your furnace immediately and contact an HVAC professional. Do not ignore this warning — carbon monoxide is odorless, colorless, and deadly. This requires immediate attention to ensure your family's safety.

Rising energy bills without a change in thermostat settings indicate your furnace is losing efficiency. Common causes include: a clogged air filter; dirty burners; a failing blower motor; a cracked heat exchanger; or an aging furnace (over 15 years old). A professional tune-up can restore efficiency by 5-15%. If your furnace is old, replacement with a 96% AFUE model may be more cost-effective.

Squealing or screeching typically points to blower motor issues — worn bearings, a loose belt, or motor failure. This reduces airflow and heating efficiency. If ignored, the motor can seize completely, requiring full replacement. Turn off the furnace and call for repair to avoid a complete breakdown during cold weather. Most blower motor issues can be fixed before complete failure.

Replace your furnace if it's over 15 years old, requires repairs costing 50%+ of a new unit's price, has a cracked heat exchanger, or needs frequent repairs. Repair if it's under 10 years old and the issue is minor (flame sensor, ignitor, belt). Apply the 5,000 Rule: repair cost x age. If over $5,000, replace. A new 96% AFUE furnace costs $3,400-$5,500 installed and saves 15-20% on heating bills.