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Furnace Not Turning On in Las Vegas: Safe Checks Before You Call
Last updated: October 26, 2026 · Reviewed by Colton Air Conditioning, NV license 0092120
Short answer: If your furnace won't turn on, check four things once: the thermostat mode and batteries, the furnace breaker, the filter, and the furnace door. If the gas was shut off, do not relight it yourself. If you smell gas, leave the house and call Southwest Gas or 911 from outside.
If you smell gas or a CO alarm sounds: leave the house and call Southwest Gas or 911 from outside. Do not flip switches or restart the furnace.
Why Las Vegas furnaces fail to start in fall
A Las Vegas furnace sits unused most of the year. NOAA's 1991–2020 normals put the average January low at 40.5°F, so the first cold mornings are often the first time the furnace has been asked to run in months. If heat starts but runs poorly, see heater not working.
The four checks (do each once)
- Thermostat mode and batteries. Confirm the mode is Heat, not Cool, Off or Fan. A blank or dim screen usually means dead batteries; replace them and check the mode again. After an outage, a smart thermostat may have lost its schedule or Wi-Fi.
- Breaker. Find the breaker labeled furnace, FAU or HVAC. If it sits in the middle, push it fully off, then on. Reset it once. If it trips again, leave it off and call.
- Filter. A packed filter can make the furnace shut itself down on its safety limit. Replace it if it's dirty. See air filter size.
- Furnace door switch. Most furnaces have a safety switch that keeps them off when the front panel is loose or off. Make sure the panel is seated and latched. Do not open the burner compartment or tape the switch.
Then stop. Do not keep cycling power or pressing reset buttons.
Furnace not turning on after summer
Months of idle dust, a filter that pulled cooling air all summer, and thermostat batteries that died unnoticed are the usual reasons. Do the four checks. If the burners still won't light, see furnace flame sensor and first heat check.
Furnace not turning on after a power outage
Outages and the surge when power returns can trip the furnace breaker or reset the thermostat. Check the breaker and thermostat first. If the furnace shows a blinking light and won't start, note the blink pattern (the legend is usually on the panel door) and call.
Furnace not turning on with the thermostat
If the thermostat is on Heat with fresh batteries and nothing happens, the problem may be the thermostat, its wiring or the furnace control. See thermostat not working.
Furnace not turning on but the fan works
A blower that runs with no heat usually means the burners aren't lighting or the furnace is locked out after failed tries. One cause is a dirty flame sensor; others include the ignitor and pressure switch (pressure switch guide). These are not homeowner repairs. Call (702) 738-6976 to schedule.
Furnace not turning on after the gas was shut off
If Southwest Gas or anyone else shut off gas to the house, do not relight the furnace or turn the gas back on yourself. Contact Southwest Gas to restore service. Once gas is back on and the furnace still won't start, call (702) 738-6976 to schedule.
Furnace not lighting
Clicking with no flame, or a flame that lights and goes out in seconds, points to the ignitor, flame sensor, gas supply or a lockout. Older units: see furnace pilot light. Don't keep retrying ignition.
Serving the southwest and Henderson side of the valley
We serve homes in Southern Highlands, Inspirada, Anthem, Silverado Ranch and Spring Valley. Call (702) 738-6976 to schedule.
FAQ
Why won't my furnace turn on after summer?
Usually dead thermostat batteries, a packed filter or a tripped breaker after months idle. Do the four checks once, then call.
Why won't my furnace turn on after a power outage?
The returning power can trip the furnace breaker or reset the thermostat. Check both once. If it still won't start, call.
The fan runs but there's no heat. Why?
The burners likely aren't lighting or the furnace is in lockout. That's a service call, not a DIY fix.
The gas was shut off. Can I relight the furnace?
No. Have Southwest Gas restore service, then call us if the furnace still won't start.
Is it safe to keep pressing the reset button?
No. Repeated resets can hide a real fault. Try the four checks once, then call (702) 738-6976 to schedule.
What if I smell gas?
Leave the house and call Southwest Gas or 911 from outside.