10 Signs Your Furnace Needs Repair
Grand Strand winters are mild, which means furnace problems hide until the coldest night of the year. Know the warning signs before that night arrives.
Most Grand Strand homes heat with heat pumps or electric air handlers, but gas furnaces are common too — especially in Conway, Aynor, and Loris where gas service runs. And because our furnaces sit idle eight months a year, problems develop silently. Here's what to watch for when heating season arrives.
Safety first: if you smell rotten eggs (natural gas odorant) or suspect carbon monoxide (headaches, nausea, dizziness when the heat runs), leave the house and call your gas utility or 911 from outside. Then call us. Those two signs skip the rest of this list.
The 10 warning signs
Roughly ordered from "schedule soon" to "call now":
1. Higher heating bills with no cold snap to blame
A gradual climb in winter electric or gas bills — without a change in rates or weather — means efficiency is slipping. Common culprits: a dirty burner, failing blower motor, or a heat exchanger losing integrity.
2. Short cycling
Furnace fires up, runs a few minutes, shuts off, repeats. Short cycling wears parts fast and never quite heats the house. Causes range from a dirty flame sensor (cheap fix) to an overheating heat exchanger (serious).
3. Some rooms hot, others cold
Uneven heating points to ductwork issues, a struggling blower, or a furnace that's lost capacity. If it heated evenly last winter and doesn't now, something changed — find out what.
Hearing new noises from the furnace?
Furnaces rarely fail without warning — they warn. If yours is talking, let a technician listen before a small problem becomes a no-heat night.
4. New noises: banging, rattling, squealing
Banging at startup can mean delayed ignition (gas buildup igniting at once — get this checked). Rattling suggests loose panels or ductwork. Squealing usually means a blower belt or motor bearing on its way out. Popping from ductwork expanding is often harmless; metallic banging from the furnace is not.
5. Yellow or flickering burner flame
A healthy gas flame burns blue and steady. Yellow, flickering, or lazy flames can indicate incomplete combustion — which can produce carbon monoxide. This is a call-now sign, not a wait-and-see one.
6. Frequent cycling of the blower without heat
Blower runs, no warm air, shuts off, repeats — the furnace is trying and failing to complete a heating cycle. Could be a failed ignitor, flame sensor, or control board.
7. Musty, burning, or metallic smells
A dusty burning smell on first fall startup is normal (dust burning off) and should fade within hours. Persistent burning, electrical, or metallic smells are not normal. Musty smells suggest mold in the system or ducts — common after our humid summers.
8. The furnace is 15+ years old and needs frequent repairs
One repair is maintenance. Annual repairs on an aging furnace are a replacement conversation — especially since newer equipment is significantly more efficient.
9. Visible rust, cracks, or soot around the furnace
Soot streaks, rust on the flue pipe, or visible cracks are combustion-safety red flags. Turn the system off and call. Cracked heat exchangers can leak carbon monoxide into your home's air.
10. Carbon monoxide detector alarms
This is the one that overrides everything: if the CO detector sounds, treat it as real. Get out, call emergency services, don't re-enter until cleared. Then have the furnace professionally inspected before running it again.
What a heating check actually covers
A proper fall heating inspection isn't a glance — it's combustion analysis (gas), heat exchanger inspection, safety control testing, burner cleaning, blower check, and thermostat verification. It takes under an hour and it's the cheapest insurance against a January emergency.
Wait — is your 'furnace' actually a heat pump?
A quick Grand Strand reality check: many homeowners who say "furnace" mean the indoor air handler of a heat pump system. If your outdoor unit runs in winter and your backup heat is electric strips (not gas burners), you have a heat pump — and several items on this list translate differently. Short cycling, aux-heat running constantly, and ice on the outdoor unit are heat-pump-specific symptoms with heat-pump-specific fixes.
Not sure which you have? Look at the outdoor unit on a cold day: if it's running and the air from it feels cold, that's a heat pump extracting heat. If the outdoor unit sits idle all winter while warmth comes from vents, you've likely got a furnace. When you call, telling the dispatcher which one you have gets the right technician with the right parts.
Need a pro for this?
Don't wait for the coldest night
Heating problems found in fall are cheap. The same problems found at midnight in January are not. Call for a heating check.
Frequently asked questions
My furnace smells like burning dust every fall. Is that normal?
On the first heating cycle of the season, yes — dust that settled on the heat exchanger over summer burns off, and the smell should fade within a few hours. If it persists beyond a day, or smells electrical or metallic, have it checked.
How often should a furnace be serviced?
Once a year, in the fall before heating season. Gas furnaces especially need annual combustion-safety checks — heat exchanger inspection and CO testing aren't optional.
Should I repair or replace my old furnace?
Consider replacement when repairs are frequent, the unit is 15+ years old, or a major component like the heat exchanger fails. A technician can show you the efficiency math for your specific situation.