Your furnace plays a crucial role in keeping your home warm and comfortable during the colder months. Like any mechanical system, it can develop problems that — if left unaddressed — become more expensive and disruptive over time. Understanding the most common furnace issues can help you recognize when your system needs attention and act before a minor problem becomes a complete breakdown.
Furnace Blowing Cold Air
One of the most frustrating issues homeowners face is a furnace that runs but blows cold air. Common causes include an overheating furnace that has tripped its high-limit switch, a dirty air filter restricting airflow, a pilot light or igniter failure, or a problem with the gas valve. Start by replacing the air filter — a clogged filter is surprisingly often the culprit. If the issue persists after a filter change, call a licensed heating technician.
Furnace Not Turning On
A furnace that won't start at all could have a tripped circuit breaker, a blown fuse on the furnace control board, a faulty thermostat, or a problem with the igniter or flame sensor. Check your thermostat settings (it should be set to "heat" and the temperature above the current room temperature), then check the breaker. If both are fine and the furnace still won't start, call for service — gas system diagnostics require a licensed technician.
Short Cycling (Turning On and Off Repeatedly)
If your furnace turns on, runs briefly, then shuts off before your home reaches the set temperature — and repeats this cycle — it is "short cycling." This is inefficient, hard on the system, and usually indicates one of the following: a clogged air filter, an oversized furnace, a dirty flame sensor, or an overheating problem. Short cycling dramatically shortens furnace lifespan and should be diagnosed promptly.
Unusual Noises
It's normal for a furnace to make some sound during startup and operation. However, loud or new sounds are warning signs:
- Banging on startup: Delayed ignition — gas builds up before igniting. Can indicate a dirty burner or gas pressure issue.
- Rattling: Loose panels, ductwork, or internal components.
- Squealing or whining: A failing blower motor bearing or worn belt (in older belt-drive systems).
- Rumbling after shutdown: Residual combustion in the heat exchanger — may indicate a cracked heat exchanger, which is a safety concern.
Furnace Not Producing Enough Heat
If your furnace runs continuously but the house never reaches the set temperature, consider whether the filter is clean, whether vents in unused rooms are closed (restricting airflow), whether ductwork has leaks, or whether the furnace is simply undersized for the home. In older Coquitlam homes that have had additions or insulation improvements, the original furnace sizing may no longer match the load.
When to Call a Professional
Many furnace problems require professional diagnosis with combustion analyzers, gas pressure gauges, and electrical diagnostic equipment. Do not attempt to repair gas components yourself — improper repairs create carbon monoxide and fire risks. If you have any doubt, call a licensed TSSA-compliant heating technician.
At Hippo Plumbing and Heating, our experienced technicians are equipped to handle all types of furnace repairs in Coquitlam and the Tri-Cities. If you're experiencing any furnace issues, don't wait — call us at (604) 365-0812 for expert service and reliable solutions.