Safety first
If you smell natural gas or propane, do not flip switches or light pilots. Leave the building, avoid using phones or garage door openers inside, and contact your gas utility or emergency services from a safe location. For carbon monoxide detector alarms, leave immediately and get help.
1. Thermostat, power, and gas supply
- Mode set to HEAT and target temperature several degrees above the current room reading.
- Fresh batteries in battery-powered thermostats.
- Furnace power switch (often looks like a light switch near the unit) in the ON position.
- Breaker labeled furnace/air handler not tripped.
- Gas shutoff valve handle parallel to the pipe (open) on gas furnaces.
2. Filter and airflow
A packed filter can cause overheating and safety lockouts. Upstate pollen seasons clog filters faster than many homeowners expect. Swap in a clean filter, open supply and return vents, and try again after a few minutes.
3. Common parts that fail
- Hot surface ignitor: cracks with age; furnace may try to start then shut down.
- Flame sensor: dirty sensors shut the gas valve for safety; cleaning or replacement is common.
- Inducer motor or pressure switch: especially on high-efficiency furnaces that need clear venting.
- Limit switch lockout after overheating from restricted airflow.
- Heat pump outdoor unit issues if your “furnace” is actually a heat pump with backup strips.
No heat tonight?
We prioritize heating emergencies across Greenville and the Upstate. Call (864) 479-6737 or request service online for the fastest available tech.
4. Heat pump homes: a quick note
Many Upstate homes heat with a heat pump, not a gas furnace. If the outdoor unit is iced over or silent while the indoor fan runs, you may need a defrost or outdoor repair, not “furnace” parts. Describe what you hear and whether you have gas or electric heat when you call so we bring the right parts.