The first-cold-front checklist
Five minutes, no tools. If the furnace runs after any of these, you have your answer; if it does not, you have a better description for the tech.
- Thermostat on HEAT, setpoint above room temperatureMost Houston thermostats have not been touched since March. Heat pump owners: EMERGENCY HEAT is not the setting you want.
- The furnace switchA light switch on or near the unit, often in the attic or a hall closet. Someone turned it off in April to stop the blower running; nobody turned it back on.
- The filterA filter packed with eight months of Gulf-coast dust starves the heat exchanger of airflow, the limit switch trips on overheat, and the furnace shuts down before the house warms. Looks exactly like "no heat."
- Dust burn-off versus a real smellTwenty minutes of hot-dust smell on the first firing is normal. A smell that persists, or that is plastic or electrical, is not. Gas smell: stop reading, go outside, see the box below.
- The condensate trap on a high-efficiency furnaceIf the flue is white PVC, the furnace makes water and has a trap. A Houston summer grows enough algae in that trap to block it; the pressure switch never proves and the furnace locks out. It is the single most common Houston-specific furnace fault.
Heating in a cooling city
Houston averages about 1,220 heating degree days a year against 3,280 cooling degree days (NOAA normals, climate zone 2A). The furnace runs from a first front in late November through a handful of cold weeks in January and February. That short season is the whole problem: the ignitor cracks on its first thermal shock of the year, the flame sensor is coated with a summer's oxide, and the blower capacitor has already been cooked by the AC side.
Calls arrive in bursts, not a curve — the evening of every Arctic front, and hard. The February 2021 storm is the reference point every Houston contractor still uses: days below freezing, rolling outages, and thousands of furnaces that would not relight after the power came back because their boards, ignitors and condensate traps had frozen. If you get one lesson from that week, it is to test the furnace in October, not on the night the front arrives.
Where in Houston
The network covers Harris County and the ring around it: The Woodlands, Spring and Cypress to the north and northwest; Katy west; Sugar Land and Missouri City in Fort Bend County; Pearland and League City south; Pasadena and Baytown east. Inside the loop — the Heights, Montrose, Bellaire, Meyerland — and the 1970s–90s stock in Spring Branch, Alief and Clear Lake are all in coverage.
Most Houston homes heat with a gas furnace inside the same closet or attic air handler as the AC coil; a growing share of newer builds in Katy, Cypress and Pearland use a heat pump with electric backup strips instead. Tell us which you have. A heat pump that blows cool air for a few minutes in heat mode is defrosting and is fine; a gas furnace that blows cool air is not.
What fails in Houston furnaces
- Flame sensor
- A rod that proves the flame so the gas valve stays open. Eight months of humid idle time coats it with oxide; the furnace lights, runs three to five seconds, and dies. Repeats three times, locks out. Cleaning fixes it more often than replacement does.
- Hot surface ignitor
- Ceramic. Cracks on the first heat cycle of the year after a summer of vibration from the shared blower. Sequence runs, gas valve clicks, nothing lights. The most common furnace repair everywhere, and Houston's first-front special.
- Condensate trap and pressure switch
- On 90-plus-percent furnaces. Algae blocks the trap, the inducer cannot pull a vacuum, the pressure switch never closes, the board locks out. The switch is usually fine; the trap is the fault.
- Limit switch trips on airflow
- A filter that went the whole AC season, or a return blocked by storage in the attic. The furnace overheats, shuts down, restarts, repeats — short cycling.
- Heat exchanger past its life
- Houston furnaces run few hours but sit in attics at 140°F all summer; corrosion from the humid idle time, not run time, ends them. Past 15 years, combustion analysis before anyone relights it.
Gas smell or CO alarm in Houston
Out of the house first, then call. CenterPoint Energy is the gas utility for most of Harris County and runs a 24-hour gas-leak emergency line; 911 works too. Do not touch light switches or the thermostat on the way out. A carbon monoxide alarm means the same thing: everyone outside, including anyone who "feels fine," and the furnace stays off until the exchanger and venting are tested with instruments.
Permits and licensing
A furnace repair needs no permit. A furnace replacement inside the City of Houston needs a mechanical permit issued through the Houston Permitting Center; anything that changes gas piping or venting goes with it. The Woodlands, Katy, Sugar Land, Pearland and League City issue their own permits.
Texas licenses HVAC contractors through the TDLR Air Conditioning and Refrigeration program. Every contractor in this network holds one; the number is searchable on that site.
What CenterPoint pays
CenterPoint Energy is both the gas and the electric delivery company across most of the metro. Its residential efficiency incentives on the electric side apply to heat pumps and high-efficiency cooling installed through a participating contractor, starting at $200 for equipment at 15.2 SEER2 or better. That matters when a furnace repair turns into a "replace the whole system with a heat pump" conversation, which in Houston's mild winters is often the right one. Current programs are listed on the CenterPoint Energy efficiency page. The federal 25C credit ended for equipment placed in service after 2025.
Furnace repair costs in Houston
Houston labor sits at the low end of the five metros. Diagnostic usually credited toward the repair; first-front evenings carry a premium because every truck is out.
| Repair | Notes | Houston range |
|---|---|---|
| Diagnostic | Sequence of operation, sensor, ignitor, pressures | $75–$140 |
| Flame sensor clean or replace | The cheapest real fix there is | $80–$220 |
| Hot surface ignitor | Techs carry them | $140–$330 |
| Condensate trap clear, pressure switch test | High-efficiency units | $120–$300 |
| Limit or rollout switch | Find the airflow cause first | $140–$300 |
| Inducer motor | Bearings or cracked wheel | $380–$850 |
| Blower motor | Shared with the AC — you have been paying for it all summer | $380–$1,100 |
| Control board | Diagnosed by outputs, not by swapping | $380–$950 |
| Gas valve | Licensed tech only | $280–$650 |
| Heat exchanger | Past 12–15 years it is a new-furnace or heat-pump decision | $1,400–$3,200 or replace |
Most Houston no-heat calls trace back to a furnace nobody looked at since the previous winter. What an October heating check in Houston actually includes, and what it costs. The full urgency-ranked fault list for any metro is on the furnace repair page. Freeze warnings: National Weather Service Houston/Galveston.