Furnace troubleshooting, in order
Furnace Won’t Turn On? Pueblo Troubleshooting Guide
Work through these in order.
- Price before any work starts
- Furnaces, heat pumps, boilers & AC
- Every ZIP from 81001 to 81012
The first five you can check yourself in a few minutes. The rest — igniter, pilot, flame sensor, pressure switch — are where our technicians come in.
Checks you can do yourself
1. Thermostat
Make sure it’s set to Heat and the setpoint is a few degrees above the current room temperature. Weak or dead batteries can keep a thermostat from signaling the furnace — replace them if it uses batteries.
2. Power: furnace switch, breaker, outage
Furnaces have a service switch that looks like a light switch, on the side of the furnace or on a nearby wall or joist. It has to be on. Then check the breaker panel: reset a tripped furnace breaker once, and if it trips again, leave it off and call.
A gas furnace needs electricity for its blower, igniter and controls, so it won’t run during a power outage. In the City of Pueblo that’s Black Hills Energy; in Pueblo West, Black Hills Energy or San Isabel Electric. Black Hills now uses wildfire-related Public Safety Power Shutoffs on high-wind days, including one that cut power to part of North Pueblo for about four hours in February 2026.
3. Filter
A clogged filter starves the furnace of air. It overheats, and its safety controls shut it down. If the filter is gray and packed, replace it and try again.
4. Gas supply
The gas shutoff valve on the pipe near the furnace is open when its handle runs parallel to the pipe. If none of your gas appliances work, the problem may be the gas supply — call your gas company (Xcel Energy inside the city) rather than relighting anything. If you smell gas, get out first.
5. Vent pipes and condensate drain
High-efficiency furnaces (90%+) vent through two plastic pipes, often on an outside wall. After snow, ice or freezing fog, check that the openings are clear. Lennox tells owners to do exactly this after any heavy snow or ice event. These furnaces also make water: if the condensate drain or trap clogs or freezes, a safety switch keeps the burners off. Water around the base of the furnace is a clue.
Where a technician takes over
If the checks above didn’t fix it, the cause is usually one of these. Look through the furnace door window for a blinking light first — the flash pattern often names the failed part, and it saves time when you call.
Igniter
Most modern furnaces light with a hot-surface igniter that glows like a stove element, or with a spark igniter. When an igniter cracks or burns out, the furnace goes through its startup but never lights. Replacing it is a quick repair for a technician.
Typical U.S. range to replace a furnace igniter: $100–$250, per HomeGuide, Nov 2026. That’s a national range, not a Pueblo quote — you get the exact price after diagnosis.
Pilot light (older furnaces)
Older furnaces keep a small standing pilot flame burning, watched by a thermocouple. If the pilot won’t stay lit, the thermocouple or the gas valve is usually to blame. Relighting it over and over isn’t a fix.
Flame sensor
If the furnace lights for a few seconds and then shuts off, a dirty flame sensor is the first thing to check. A thin coating on the sensor rod keeps it from “seeing” the flame, so the control shuts the gas off. A furnace burning rich because its gas input was never adjusted for Pueblo’s altitude can make soot (ACHR News), and residue on the rod is exactly what blinds the sensor — so a good repair checks the setup too.
Pressure switch and inducer
Before lighting, the furnace runs its small inducer fan, and a pressure switch confirms the exhaust is venting. A blocked vent, a cracked or clogged switch hose, a failing inducer motor or a bad switch keeps the furnace from going any further. If your furnace was set up with a high-altitude kit, a replacement switch has to be the high-altitude version.
Rollout switch
Some furnaces have a rollout switch with a manual reset button near the burners. It trips when flames or heat escape where they shouldn’t. If it trips again after a reset, don’t keep resetting it — call us, because the cause needs to be found.
Control board, gas valve, motors
Less often, the control board, the gas valve or the blower motor has failed. These are diagnosed with a meter, not by guessing, and we’ll tell you the price before replacing anything.
Questions we hear
The furnace clicks but never lights. What does that mean?
Clicking without a flame usually points to the ignition system or the gas supply — a failed igniter, a dirty flame sensor, or gas not reaching the burners. Check that the gas valve near the furnace is open and that your other gas appliances work. If they do, call us; igniters and gas valves are technician work.
I can hear the small fan run, then everything stops.
That small fan is the inducer. If it runs but the burners never light, the pressure switch may not be confirming draft — often because a vent pipe is blocked by snow or ice, or the switch’s rubber tubing is clogged or cracked — or the igniter isn’t doing its job. Clear the outside vent pipes, reset once, and call us if it repeats.
Can I jumper the pressure switch to get heat tonight?
No. The pressure switch is a safety control that keeps the furnace from firing when exhaust isn’t venting properly. Lennox states plainly that it must never be bypassed — doing so can let the furnace run without proper venting. Call us instead — we answer 24/7.
How do I relight a pilot light?
Only older furnaces have a standing pilot; most furnaces made since about 2010 use an electronic igniter instead. If yours has a pilot, follow the lighting instructions on the furnace label exactly. If it won’t stay lit, the thermocouple or gas valve may be failing — call us rather than trying again and again. If you smell gas at any point, stop and get outside.
Why does the breaker keep tripping?
Resetting it once is fine. If it trips again, the problem is most likely in the furnace itself, not the panel. Leave the breaker off and call us.
Furnace still won’t start? Call us.
We answer 24/7 for Pueblo and Pueblo West. Tell us the blink code if you have it, and our licensed & insured technicians will take it from there.
Where the Pueblo facts on this page come from
Checked against these public sources on November 3, 2026. Weather figures are National Weather Service records for Pueblo Memorial Airport.
- NWS Pueblo — seasonal snowfall
- City of Pueblo — online payments (Black Hills Energy electric, Xcel Energy gas)
- KKTV — Black Hills Energy public safety power shutoff, Feb 2026
- Carrier — furnace not turning on
- Trane — furnace not igniting
- Lennox — user’s manual (vent pipes after snow; pressure switch must not be bypassed)
- ACHR News — high-altitude furnace modifications
- HomeGuide — How Much Does Furnace Repair Cost? (2026), typical U.S. price ranges (checked Nov 2026)