Why is my furnace not heating?
A furnace that won't heat is most often a dirty filter choking airflow, a failed igniter, or a thermostat problem — in that order of cheapness. A furnace that starts, runs a minute, then stops is usually a dirty flame sensor. True no-heat in deep cold justifies the after-hours call; a mild-weather failure usually doesn't.
Likely causes
- Clogged filter — Restricted airflow overheats the furnace until the safety switch shuts it down.
- Failed igniter — Modern furnaces light with a hot-surface igniter that cracks every 5–7 years. Clicking with no flame points here.
- Dirty flame sensor — The furnace lights, runs a minute, and quits — the sensor can't prove flame, so it shuts down safely.
- Thermostat or power issue — Dead thermostat batteries, a tripped breaker, or an open furnace door switch — check before you pay for a visit.
What you can check yourself
- Replace the filter, and confirm the thermostat is on 'heat' with fresh batteries if it uses them.
- Check the breaker and the furnace's own power switch (it looks like a light switch, usually near the unit).
- Make sure the furnace access door is fully closed — many units won't run with the door switch open.
Typical cost
Typical repairs in Charlotte, NC: service call $100–$250; igniter $150–$350; flame sensor cleaning/replacement $150–$300; blower motor $400–$800.
When to call a pro
Gas smell, a carbon monoxide alarm, or a furnace that short-cycles with a burning smell — leave and call from outside. Otherwise, no heat below ~40°F with kids or elderly at home counts as urgent.
HVAC pros in Charlotte, NC
- Winston Comfort Systems · 360 S Graham St, Charlotte, NC · +17049989848
- Service Logic · 650 S Tryon St Ste 1000, Charlotte, NC · 9802961700
- Charlotte · 1530 Elizabeth Ave, Charlotte, NC · 19803019528
- Yandle-Witherspoon Supply · 1001 N Brevard St, Charlotte, NC · +17043424389
- Lindsay Heating & Air Conditioning · 2339 Lucena St, Charlotte, NC · 17043471847
- Assured Quality Llc · 3637 N Graham St, Charlotte, NC · 17044921165
- Advanced Mechanical · 3800 Woodpark Blvd, Charlotte, NC · +17042388756
- Dealers Supply Co. · 3731 Woodpark Blvd n, Charlotte, NC · +17044059900
Get free quotes from Charlotte, NC pros →
Data by Servik — verified local pros from official license records and public sources. Cost figures are typical ranges, not quotes; a pro's written estimate is the real number.