Heater not working? What to check before you call

Last checked October 29, 2026

Las Vegas nights drop to a normal low around 47°F in November and 40°F in December, so the heat usually kicks on for the first time this time of year. If yours won't, here's what the manufacturers tell homeowners to check.

Check these first

1. Thermostat. It needs power, should be set to Heat (not Off or Cool), and set higher than the room temperature. If it runs on batteries, replace them. (Carrier)
2. Breaker. Look for a tripped breaker labeled furnace or HVAC. Switch it fully off, then back on. (Carrier)
3. Furnace power switch. It looks like a regular light switch, on or near the furnace. Someone may have flipped it off by mistake. (Carrier, Emerson)
4. Front panel. Many furnaces have a door switch that cuts power when the panel is off or loose. Make sure it's seated tight. (Carrier)
5. Filter. A dirty filter restricts airflow, and the furnace can overheat and shut itself off for safety. Carrier says to check it about every 4 weeks. (Carrier)
6. Gas valve. The handle on the gas line to the furnace should be parallel to the pipe, which means open. (Carrier)
7. Blinking light. Most furnaces have a light on the control board that blinks a code. What it means depends on your make and model. Write down the pattern and tell the tech, but don't attempt the repair yourself. (Trane)
8. Water around the furnace. High-efficiency furnaces (90% and up) make condensation. If the drain line clogs, water can back up and leak. (Carrier)

Got an older furnace with a standing pilot light? Follow your owner's manual. Trane says to turn the gas knob off and wait about 5 minutes for the gas to clear before relighting. If the flame is yellow or the pilot won't stay lit, call a pro.

Things that look wrong but are normal

• Burning smell the first time it runs. Trane says that's usually dust burning off and it should clear on its own. If the smell lasts more than an hour, gets worse, or smells electrical, turn it off and call.
• Steam off the heat pump. Heat pumps go into defrost mode in cold weather. You may see steam rise from the outdoor unit, the fan may stop and you may hear a swoosh. Each cycle is about 3 to 5 minutes. (Trane)
• "Aux heat" on the thermostat. That's backup heat helping when the heat pump can't keep up on its own. Emergency heat is when you run that backup heat by itself. (Lennox)

When to stop and call

• You smell gas. Leave right away. From a safe place, call 911 and Southwest Gas at 877-860-6020, day or night. Don't flip switches, touch the thermostat or try to relight anything.
• Carbon monoxide symptoms. Southwest Gas lists flu-like symptoms, dizziness, headache, nausea, shortness of breath and confusion. Get everyone to fresh air and call 911.
• No CO alarm? NFPA says to put one outside each sleeping area and on every level of the home.
• Never heat the house with a gas oven or grill. The CDC warns against it because of carbon monoxide.
• If you've checked the list and it still won't run, it's time for a tech. Southwest Gas recommends having gas appliances serviced every year by a trained pro.

What a repair costs here

A Las Vegas HVAC company says most furnace repair visits run $160 to $400. Nationally, an igniter runs $150 to $250 and a flame sensor $75 to $250. See all the numbers on furnace repair and replacement prices, and check any quote with the quote checker.

Common questions

Sources

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