In the Las Vegas Valley, the furnace can sit unused for six months or more. It runs one last cycle in spring, then the AC carries the house through a long, hot summer. When the first cool night of fall arrives, you set the thermostat to heat, and… nothing happens.
Don’t panic. A furnace that won’t start after summer is one of the most common fall calls, and often the cause is simple. Below are seven safe checks any homeowner can do in about 15 minutes. You’ll also find the warning signs that mean you should stop and call a pro.
Safety first: If you smell gas (a rotten-egg odor), don’t flip switches or try to restart anything. Leave the house and call 911 or your gas utility from outside. If your carbon monoxide alarm sounds, get everyone outside and call 911.
1. Check the thermostat settings
It sounds obvious, but this one gets everybody. After months on “Cool,” the thermostat needs to be switched to Heat, and the set temperature has to be a few degrees above the current room temperature. If yours is a smart thermostat, check whether a schedule or “eco” setting is overriding you.
Also look at the screen. A blank or fading display usually means dead batteries. Replace them and give the system a few minutes to respond.
2. Look at the breaker and the furnace power switch
Your furnace needs electricity even if it burns gas. Check your electrical panel for a tripped breaker labeled “furnace,” “FAU,” or “air handler,” and reset it once if it’s tripped.
Next, find the furnace’s service switch. It usually looks like a regular light switch on or near the furnace, in the garage, a closet, or the attic. It’s easy to bump off by accident, especially if something was stored nearby over the summer.
If the breaker trips again right away, don’t keep resetting it. That points to an electrical problem that needs a technician.
3. Make sure the furnace door is closed tight
Most furnaces have a safety switch behind the front access panel. If the panel is loose or crooked, even slightly, the furnace won’t run. Push it firmly into place and make sure it’s latched.
4. Replace a clogged filter
A long Las Vegas summer pushes a lot of dust through your system, since the same filter often serves both your AC and your furnace. A badly clogged filter chokes airflow. Many furnaces will overheat and shut themselves off as a safety measure, or never start at all.
Pull the filter and hold it up to a light. If you can’t see light through it, replace it. If you’re not sure which size or type your home needs, our filter replacement service can take care of it.
5. Confirm the gas supply is on
Most furnaces have a gas valve on the supply line next to the unit. The handle should run parallel to the pipe when it’s open. If other gas appliances in your home work, such as a stove or water heater, your gas service is likely fine.
If you aren’t comfortable around gas lines, skip this step and call us. Never try to relight or adjust gas components yourself unless your owner’s manual specifically tells you how.
6. Check the condensate drain (high-efficiency furnaces)
High-efficiency furnaces make water as they run and drain it through a small PVC line. Many have a safety switch that shuts the furnace down if that line backs up. Over a dry Las Vegas summer, sediment, dust, or even insects can build up in it. Look for water around the base of the furnace or a full condensate pan. Either is a sign the drain needs to be cleared.
7. Read the blinking light
Many modern furnaces have a small window on the lower panel with a status light. A blinking pattern is a diagnostic code, and the chart that explains it is usually on the inside of the furnace door. Write down the pattern before you call. It helps our technician arrive with the right parts and can shorten the visit.
When to stop and call a professional
Call a licensed technician instead of troubleshooting further if you notice any of these:
- The furnace starts, then shuts off after a few minutes, over and over
- A burning or electrical smell that doesn’t fade (a light dusty smell for the first few minutes is often normal. See our post on normal first-startup smells)
- Loud banging, squealing, or grinding
- The blower runs but only cold air comes out
- The breaker keeps tripping
- Any gas smell, or your carbon monoxide alarm goes off (get out first, then call)
These usually mean a failed igniter, a dirty flame sensor, a bad blower motor or capacitor, a control board issue, or a safety device doing its job. None of these are DIY repairs.
Why a fall tune-up prevents most of this
Most “won’t turn on” calls trace back to small things a tune-up catches early: a weak igniter, a dirty flame sensor, a clogged drain, a loose wire. A furnace tune-up before the first cold snap means your heat works the night you need it, not the morning after.
If you’d like that handled for you every year, the 32 Degrees Membership Club includes scheduled maintenance visits. Desert Ready includes one combined heating and cooling inspection a year, and Desert Guardian includes a spring cooling visit plus a fall heating visit. Members also get discounts on eligible repairs and scheduling priority. Plan visits are scheduled before May 15 or after September 15, so fall is the right time to book.
Need help now? We’re local and answer 24/7.
Whether you’re in North Las Vegas, Henderson, Summerlin, or anywhere in the Las Vegas Valley, 32 Degrees is a repair-first team. We find the real problem, explain your options, and get approval before any work starts.
📞 Call or text 702-635-9505 or Book Now for furnace repair in Las Vegas. For a no-heat night, our 24/7 emergency service is a phone call away.
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