To reset your furnace after a power outage, turn the thermostat to OFF, switch the furnace's power disconnect to OFF, wait 30 seconds, restore power, then set the thermostat back to HEAT and watch for the igniter to fire within about 90 seconds. If the burners light and stay lit, you're done. If the furnace goes through three failed ignition cycles and locks out, the reset button on the blower compartment won't fix it - that's a component problem.
Most Colorado outages are short. Xcel Energy crews restore the grid in a few hours, but the furnace doesn't always come back on its own. The control board holds a fault code, the thermostat has lost its schedule, or a safety switch tripped when the blower stopped mid-cycle. Below is the exact sequence our technicians run on service calls, plus the failures that mean you should stop and call someone.
Why Your Furnace Shuts Down After an Outage
A furnace shutdown after a power outage is a safety response, not a malfunction. Modern furnaces run a startup sequence every time they fire: the inducer motor spins up, the pressure switch closes, the igniter glows, the gas valve opens, the flame sensor proves flame, and the blower starts. If any step fails, the board shuts the gas valve and tries again. After three failed attempts, it locks out for one hour.
An outage interrupts that sequence mid-cycle. The board loses its place, the thermostat loses its 24-volt signal, and the flame sensor reads no flame because there isn't one. The furnace is doing exactly what it was designed to do - it's waiting for you to clear the fault.
Colorado adds a wrinkle. Our temperature swings are brutal - a 60-degree afternoon in November can drop to 15 degrees by 2 a.m. When the power comes back at 3 a.m. and the furnace locks out, you wake up to a 48-degree house. That's the call we get most often from Furnace Repair in Aurora and the surrounding metro, where 1970s and 1980s furnaces are still common and their control boards are less forgiving than newer models.
How Do I Reset My Furnace After a Power Outage in Colorado?
The reset sequence for a furnace after a power outage in Colorado is the same whether you have a gas, electric, or high-efficiency unit: kill power at the thermostat and the furnace, wait, restore, and let the board run its startup cycle. Here's the order that works.
- Turn the thermostat to OFF. Not HEAT, not AUTO - OFF. This clears the call for heat so the board doesn't try to fire while you're working.
- Find the furnace power switch. It's a standard light switch on the side of the furnace or on a nearby wall. Flip it OFF.
- Kill the breaker. Go to your panel and switch the furnace breaker to OFF. This is the step most homeowners skip, and it's the one that actually clears a locked control board.
- Wait 30 seconds. Not 5. The board needs time to drain its capacitors and forget the fault code.
- Restore the breaker, then the furnace switch, then the thermostat. Reverse order. Thermostat last, set to HEAT.
- Listen for the inducer. Within 30 to 60 seconds you should hear a small fan spin up. Then a click. Then the igniter glows orange for 15 to 20 seconds. Then the burners light.
- Watch the blower. Warm air should reach your registers within 2 to 3 minutes. If the burners light and shut off within 5 seconds, the flame sensor is dirty or failed.
If the furnace fires and runs, set your thermostat schedule back up. Most smart thermostats lose their programming during an outage and default to a 62-degree setback, which is why your house feels cold even though the furnace is working.
Where Is the Furnace Reset Button Located?
The furnace reset button location depends on the furnace type. On most gas furnaces, the reset button is a small red or black button inside the blower compartment, on the burner side, near the control board. You'll need to remove the lower access panel to reach it. On older furnaces, there's also a rollout switch - a small manual-reset button near the burners that trips if flames roll out of the combustion chamber.
On electric furnaces, the reset is usually a breaker on the unit itself or a high-limit switch near the heating elements. On high-efficiency condensing furnaces, there's often a reset on the condensate trap or pressure switch assembly.
Before you press anything, know this: the reset button is a safety device, not a fix. If it trips once after an outage, pressing it is reasonable. If it trips twice in a week, something is wrong - a cracked heat exchanger, a blocked flue, or a failing inducer motor. Pressing it a third time doesn't reset the furnace, it just delays the diagnosis.
If you can't find the reset button or the panel won't come off cleanly, don't force it. Call us and we'll walk you through it or send a technician. We do this on hundreds of Furnace Repair in Colorado calls every winter.
Why Won't My Furnace Turn On After a Power Outage in Colorado?
A furnace that won't turn on after a power outage in Colorado is usually locked out on a fault code, not broken. The board is waiting for a reset it can't perform on its own. But there are five failures that look like a lockout and aren't.
1. The thermostat lost its batteries or programming
Battery-powered thermostats drain fast during an outage if they're trying to hold a schedule. If the display is blank or showing a low-battery icon, replace the batteries and reset the schedule. This is the single most common cause we see.
2. The door switch is open
Every furnace has a safety switch on the blower door. If the panel isn't seated all the way, the furnace won't fire. Push the door firmly until it clicks.
3. The condensate trap is full or frozen
High-efficiency furnaces drain condensate through a trap and a PVC line. In a Colorado cold snap, that line freezes and the pressure switch won't close. If you see ice on the exterior PVC, that's your problem. Thaw it with a hair dryer on low, or call us.
4. The flame sensor is dirty
The flame sensor is a thin rod in the burner flame path. After a power surge, it can read a weak signal and shut the gas valve within 5 seconds of ignition. Cleaning it takes 10 minutes with steel wool, but it's a live-gas job - we don't recommend homeowners do it.
5. The control board failed
Power surges kill control boards. If the board has a burnt smell, a visible scorch mark, or no LED activity at all, it's done. A replacement board runs $250 to $600 in parts for most residential furnaces, plus labor.
If your furnace won't turn on after a power outage in Colorado and you've run the reset sequence twice, stop. Repeated resets on a board with a real fault can damage the igniter or the inducer motor, and those are $150 to $400 parts.
Common Mistakes to Avoid During a Furnace Reset
Most furnace damage after an outage comes from homeowners doing too much, not too little. Here's what we see on service calls.
- Resetting without killing the breaker. The thermostat OFF switch doesn't clear the board. You need the breaker.
- Pressing the reset button repeatedly. Three presses in an hour means something is failing. Stop and call.
- Ignoring the fault code LED. Most boards flash a code - three flashes, four flashes, etc. Write it down. It tells the technician exactly where to look and saves you diagnostic time.
- Relighting a pilot without checking for gas smell. If you smell gas, leave the house and call 911 or Xcel's emergency line before anything else.
- Assuming the furnace is broken when it's the thermostat. Swap the thermostat batteries first. It costs $4 and solves roughly a third of our post-outage calls.
- Running the furnace with a blocked flue. Snow and ice can block a sidewall vent after a storm. Clear it before you reset, or you'll trip the rollout switch again.
One more: don't skip the annual tune-up because the furnace "seems fine" after a reset. A furnace that survived an outage has been stressed. A Furnace Tune-Up in Colorado in the fall catches the flame sensor, igniter, and capacitor issues that turn into 2 a.m. no-heat calls in January.
When to Call a Professional
Call a professional if the furnace locks out twice in 24 hours, if the reset button trips again within an hour, if you smell gas, if the breaker trips when you restore power, or if the control board shows no LED activity. Those are not reset problems - they're component failures, and continuing to reset the furnace risks a cracked heat exchanger or a carbon monoxide issue.
We handle these calls every winter across the Front Range and the mountain towns. Our technicians carry control boards, flame sensors, igniters, and inducer motors on the truck, so most post-outage repairs are done in a single visit. If you're in a rural area like Furnace Repair in Bailey, where propane furnaces and well pumps share the same panel, we'll check the whole electrical path, not just the furnace.
If you're not sure whether your furnace needs a reset or a repair, call us. We'll ask three questions and tell you honestly whether to try it yourself or book a visit. Upfront pricing before we start, every time.
Frequently Asked Questions
How do I reset my furnace after a power outage in Colorado?
Turn the thermostat to OFF, flip the furnace power switch off, kill the furnace breaker, wait 30 seconds, then restore the breaker, the switch, and the thermostat in that order. Set the thermostat to HEAT and listen for the inducer fan within 60 seconds. If the burners don't light after three tries, call a technician.
Why won't my furnace turn on after a power outage in Colorado?
The most common causes are dead thermostat batteries, an open blower door switch, a frozen condensate line, a dirty flame sensor, or a control board locked out on a fault code. Check the thermostat batteries first - that solves about a third of post-outage no-heat calls. If the board shows no LED, it likely failed.
Should I call a professional if my furnace won't reset in Colorado?
Yes, if the reset button trips twice in 24 hours, if the breaker trips on restore, if you smell gas, or if the furnace locks out after two full reset attempts. Those point to a failed control board, igniter, inducer motor, or heat exchanger - all jobs that need a licensed technician and a combustion analyzer.
How long does a furnace take to come back on after a power outage?
A properly reset furnace fires within 60 to 90 seconds of the thermostat call. The inducer spins for 30 to 45 seconds, the igniter glows for 15 to 20 seconds, and the burners light. Warm air reaches your registers in 2 to 3 minutes. If nothing happens in 5 minutes, the board is locked out.
Can a power surge damage my furnace even if the power comes back on?
Yes. Surges kill control boards, blower capacitors, and variable-speed motors. If your furnace runs but the blower is weak, the board smells burnt, or the unit short-cycles every few minutes, a surge likely damaged a component. A whole-home surge protector on the furnace circuit costs $150 to $300 installed and prevents most of this.
Get Help With Furnace Repair in Colorado
If your furnace won't reset, won't stay lit, or keeps locking out after every outage, our team can diagnose it the same day. We stock the parts that fail most often after a surge or outage, so most repairs are finished in one visit.
Call Furnace Pros Colorado at (833) 588-3896 and we'll get your heat back on.