GuidesFlame sensor
Furnace Flame Sensor in Las Vegas: Why Heat Lights, Then Quits
Many Las Vegas furnaces light for a few seconds, then shut the gas off and try again. A dirty or failing flame sensor is one of the usual causes. The board needs proof of flame. Without a clean signal, it locks out for safety.
Colton Air Conditioning schedules these calls Monday–Friday, 8am–5pm.
What it often looks like
- Ignitor glows or sparks, burners light, then flame dies in a few seconds
- Blower may or may not start before the cycle ends
- Furnace retries, then stops with a flash code
- Heat worked last winter; first cold nights fail after a dusty summer
This pattern overlaps furnace short cycling and heater not working. Most modern units use electronic ignition, not a standing pilot — furnace pilot light.
What the sensor does
The flame sensor is a thin metal rod in the burner flame. It sends a tiny current to the control board when flame is present. Dust, oxidation, and a cracked insulator cut that signal. The board thinks the flame failed and closes the gas valve.
What not to do
- Do not keep resetting the thermostat to force more light attempts. That wears the ignitor.
- Do not rub the rod with sandpaper until it is thin or bent — light cleaning belongs to someone who will also check the signal.
- Do not ignore a gas smell. Leave the house, call 911 from outside, and do not flip switches.
If you smell gas or hear a hiss, get out and call emergency services. That is not a flame-sensor appointment.
Home checks that are still safe
| Check | Why |
|---|---|
| Thermostat on Heat, set a few degrees above room | Wrong mode looks like a dead furnace |
| Filter not clogged | Poor airflow causes other short-cycle faults |
| Furnace switch and one breaker reset | Power issues mimic lockouts |
| Door panel fully seated | Many units will not run with the door open |
Anything past that needs a measured look: flame signal (microamps), ignitor, gas pressure, and board codes.
What a proper call usually includes
Confirm ignition sequence, measure flame signal against the manufacturer range, clean or replace the sensor when needed, and check that the burners and ground path are sound. A “cleaned the rod” visit with no meter reading is incomplete.
Related: furnace repair Las Vegas, HVAC second opinion.
When to call
Call when heat lights and dies, the furnace locks out after retries, or first cold nights return the same fault after last year’s “quick clean.”
Have ready if you can: about how old the furnace is, whether you saw a glow then flame, and any flash-code pattern on the board.
Hours are Monday–Friday, 8am–5pm.
FAQ
Is a dirty flame sensor dangerous?
The lockout is the safety response. Forcing endless restarts is harder on parts. Gas odor is a different emergency — leave and call 911.
Can I clean the flame sensor myself?
We do not recommend DIY on the gas train. Wrong technique damages the rod and skips the signal check.
Is this the same as a pilot light going out?
Usually no. Most Valley furnaces use hot-surface or spark ignition with a flame sensor, not a standing pilot.
What hours can I reach Colton?
Monday through Friday, 8am to 5pm.
Furnace lights, then quits on a cool Las Vegas night? Call Colton Air Conditioning at (702) 738-6976 Monday–Friday, 8am–5pm. Tell us whether you saw flame before it died. We will tell you if we can see it.
Colton Air Conditioning · Las Vegas Valley residential HVAC · Monday–Friday 8am–5pm
Call (702) 738-6976 or Book Online. License 0092120. Hours Monday through Friday, 8am to 5pm. Saturday and Sunday are closed.
If we have already been out, leave a Google review.
Services
Furnace Repair Las Vegas
Furnace repair for Las Vegas homes when the desert night finally drops and the heat will not stay on.
Heating Repair
Gas furnace repair for Las Vegas homes, plus heat pumps, with the safety checks a gas system needs.
Emergency Heating Repair
No-heat calls in Las Vegas during weekday hours. Furnaces and heat pumps diagnosed before replacement talk.