Heating
Furnace Not Working During a Texas Freeze? What to Check and How to Protect Your Home
By Geaux 72 Air & HeatUpdated 6 min read
The short answer
Check the thermostat (Heat, set above room temperature), the furnace breaker and its power switch, the filter, and your gas or propane supply. Reset a locked-out furnace once by switching its power off and on. A frozen condensate line or iced PVC vent can shut down a high-efficiency furnace. If heat stays off, protect the pipes and call (321) 478-0693.
Why hard freezes knock out heat in North Texas
Heating systems here are built for mostly mild winters. A furnace that cycles a few times an hour in a normal January can run 20 hours a day when it sits in the teens. The February 2021 winter storm showed what happens next: worn igniters gave out, heat pumps iced over, condensate lines froze, power went out in rolling blocks and propane deliveries stalled on icy roads.
In town, most furnaces run on Atmos Energy natural gas. Beyond the gas mains, homes rely on propane furnaces, heat pumps or electric heat strips. The checks below cover all three.
Safe checks before you call
- 1Thermostat. Confirm it is on Heat and set a few degrees above room temperature. Replace dim or dead batteries.
- 2Breaker. If the furnace or air handler breaker has tripped, reset it once. If it trips again, leave it off.
- 3Furnace power switch. Make sure the light-style switch near the furnace is on and the door panel is seated firmly; a loose panel trips a safety switch.
- 4Filter. A clogged filter can make a furnace overheat and shut off on its high-limit switch.
- 5Gas supply. Check whether a gas water heater or range still works. Never touch the gas valve inside the furnace.
- 6Propane level. On rural properties, read the tank gauge. If it is low, call your supplier now; deliveries back up fast in a storm.
- 7Ignition lockout. A gas furnace that fails to light several times locks out. Turn the power switch off for about a minute, then back on, one time. If it locks out again, call.
If you smell gas, do not touch switches. Get everyone out first, then call Atmos Energy (or your propane supplier) and 911 from outside.
Heat pumps in a freeze: defrost or a real fault?
In freezing, damp weather the outdoor coil of a heat pump frosts over, and the system periodically runs a defrost cycle: the outdoor fan stops, the unit whooshes and steam rises for a few minutes while indoor air feels cooler. That is normal. So is "AUX" on the thermostat in deep cold, which means the heat strips are helping.
Not normal: a solid block of ice for hours, an outdoor fan that will not turn, or a house losing temperature while the strips run nonstop. Do not chip at the ice. If the unit is iced solid, Emergency Heat runs the strips alone until a technician arrives. Our heat pump repair service covers defrost boards and reversing valves.
| Symptom | Likely cause | What you can do |
|---|---|---|
| Furnace starts, then shuts off within minutes | Frozen condensate line, blocked vent, dirty flame sensor | Look for ice at the PVC drain and vent outside; call if it repeats |
| Gas furnace clicks but never lights | Ignition lockout or gas supply problem | Power cycle once; check other gas appliances |
| Heat pump steaming, outdoor fan stopped | Normal defrost cycle | Wait 10 to 15 minutes |
| Thermostat shows AUX | Heat strips assisting in deep cold | Normal; leave the setpoint steady |
| Propane furnace dead, tank gauge low | Low tank or frozen regulator | Call the propane supplier |
Frozen condensate lines on high-efficiency furnaces
A high-efficiency gas furnace makes water, which drains through a PVC line to a floor drain, a condensate pump or outside. Where that line crosses an unheated attic or exterior wall, it can freeze. Water backs up into the trap, a pressure switch senses it and the furnace shuts down. The PVC intake and exhaust pipes can also ice over.
From the ground, look where the white PVC pipes leave the house; if a low sidewall vent is packed with snow, gently clear it by hand. Never climb onto the roof. The technician thaws the line and can insulate or reroute it. Our furnace and heating repair page covers what fails first when temperatures drop into the teens.
No power, no heat: outages and iced-over vents
A gas or propane furnace still needs electricity. The igniter, the inducer motor, the control board and the blower all run on household current, so when the power goes out, so does the heat. That is what many North Texas homes learned during the rolling outages of the February 2021 storm. When power returns, set the thermostat to Off, wait a few minutes for the supply to steady, then call for heat; if the furnace runs through its start-up and still will not light, it may have locked out, and one power-switch reset is fine.
Check the white PVC pipes on the outside wall
High-efficiency furnaces breathe through two white PVC pipes that usually exit a side wall or the roof. Sleet, drifted snow or ice from a dripping eave can close them off, and the furnace shuts down on its pressure switch for safety. If you can reach them from the ground, brush away snow and loose ice with a gloved hand or a broom handle; never pour hot water on them or chip at the pipe. If they are clear and the furnace still locks out, or ice is inside the pipe, leave it for the technician.
Protect the house while you wait
- Keep supply vents open; closing them makes a struggling system work harder.
- Open sink cabinets on outside walls and let those faucets drip.
- Find your main water shutoff before a pipe bursts.
- Keep the garage door shut and open blinds on sunny south windows by day.
- Plug space heaters straight into a wall outlet, with 3 feet of clear space around them.
Never use a gas oven, range, grill or charcoal to heat the house, and run a generator only outdoors, at least 20 feet from the house. All of them can fill a home with carbon monoxide. Put CO alarms on every level and near bedrooms. If one sounds, get everyone outside and call 911 from there.
Getting help when everyone needs it at once
Our line is answered 24/7, and we confirm timing on the call based on the nearest available technician. Tell us if an infant, an older adult or someone medically fragile is in the home. Our 24/7 emergency heating repair page explains after-hours dispatch. Many 1950s homes in White Settlement have small hallway closet furnaces; see furnace repair in White Settlement, or call (321) 478-0693.
The bottom line when the heat goes out in a freeze
Most no-heat calls in a North Texas freeze trace back to something specific: a locked-out furnace, a heat pump in defrost, an iced PVC vent or condensate line, an empty propane tank or a power outage. Work through the safe checks once, keep the house closed up and the pipes protected, and never heat with an oven, grill or generator indoors. In older White Settlement and Azle homes with hall-closet furnaces, call early in a cold snap rather than late. Furnace and heating repair and 24/7 emergency service are a call away at (321) 478-0693.
From the job site
What fails after a few days of hard cold
After the February 2021 storm, the no-heat calls were not all dead furnaces. Hot-surface igniters cracked after thousands of extra cycles, worn inducer motors seized, condensate traps froze in thinly insulated attics, and heat pumps sat in rings of ice under dripping gutters. Propane customers outside Azle and Springtown ran dry because delivery trucks could not get through.
The week before a forecast freeze is when to act. Run the heat while parts houses are open, so a weak igniter shows up on a weekday instead of at midnight in the teens. Check the propane, insulate exposed condensate lines and put in a fresh filter.
- Run the heat a few days before the cold arrives.
- Top off the propane tank before the forecast hits.
- Test CO alarms and replace dead batteries.
Related questions
Is it normal for my heat pump to blow cool air when it is freezing outside?
Should I keep resetting my furnace if it keeps shutting off?
How warm should I keep the house to protect the pipes?
Can I use my gas oven to heat the kitchen while the furnace is out?
Does a gas furnace work during a power outage?
Written by the Geaux 72 Air & Heat team for homeowners in Azle and nearby communities. General information, not a diagnosis or engineering advice: leave refrigerant, electrical and gas work to a licensed HVAC technician, who has the final word on your system. Every HVAC contractor we send is licensed and insured in Texas. Last reviewed October 2026.