7 Signs Your Furnace Needs Repair Before Winter

Furnaces sit unused most of the year in South Texas, which makes it easy to miss a developing problem until the first genuinely cold night. Watch for these seven signs — or run through our full fall HVAC maintenance checklist before problems start.

1. Furnace Won't Turn On At All

Start with the basics — thermostat batteries, breaker panel, and that the system is actually set to "heat." If those check out and it still won't fire up, the issue is likely the igniter, control board, or a safety switch that needs a technician.

2. Strange Noises (Banging, Screeching, Rattling)

A bang on startup can mean delayed ignition — gas building up before it lights, which is worth having checked promptly. Screeching often points to a blower motor or belt issue; rattling can be as simple as a loose panel.

3. Weak Airflow or No Heat From the Vents

If air is moving but not warm, or barely moving at all, the cause ranges from a clogged filter to a failing blower motor or a cracked heat exchanger. This isn't one to guess at — a diagnostic visit will pin it down.

4. A Yellow or Flickering Burner Flame

A healthy gas furnace burns with a steady blue flame. Yellow, flickering, or orange flames can signal incomplete combustion and a possible carbon monoxide risk. If you see this, turn the system off and call for service — don't wait.

5. Furnace Short-Cycling (Turning On and Off Repeatedly)

Short-cycling wears down components faster and often points to a dirty filter, a failing thermostat, or a furnace that's oversized or undersized for your home.

6. A Sudden Jump in Your Energy Bill

A furnace working harder than it should to hit your set temperature shows up on your bill before it shows up as an obvious symptom in the house.

7. Your System Is 15+ Years Old

Even a furnace with no obvious symptoms yet is more likely to fail without warning once it's past 15 years. If yours is in that range, a fall inspection is worth it before you're relying on it through winter.