View source for Furnace Not Heating After a Storm: Troubleshooting Checklist

<html><p> <img  src="https://seo-neo-client.s3.us-east-1.amazonaws.com/airpro-heating-cooling/hvac%20company.png" style="max-width:500px;height:auto;" ></img></p><p> Storms do more than rattle windows. They shake up electrical grids, drive water where it doesn’t belong, and push debris into vents and intakes. When the weather calms and the furnace won’t heat, the cause is often something simple that snowballed into a shutdown. I’ve been called to dozens of these post-storm no-heat situations, and the patterns repeat. The good news is that most homes can get back to heat with a careful, safe walkthrough before calling for service. The key is methodical checks, patience between steps, and respect for safety.</p> <p> This guide follows the flow I use in the field, starting with the easy wins and moving to the issues that need a professional. It leans on practical details, not theory. If you smell gas, see scorch marks, or have standing water in or around the unit, stop and call a licensed tech or your utility. Everything else, you can approach with a quiet mind and a flashlight.</p> <h2> Why storms knock out heat</h2> <p> Furnaces sit at the crossroads of electricity, gas, combustion air, and ventilation, all of which storms disrupt. Power flickers scramble control <a href="https://online-wiki.win/index.php/Top_Reasons_a_Furnace_Is_Not_Heating_and_How_to_Fix_Them"><strong>heating and cooling repair companies</strong></a> boards and smart thermostats. Lightning and surges can punch through delicate low-voltage circuits. Heavy rain or snow blocks vents or floods basements, forcing safety switches to do their job and kill the burner. Wind drives leaves into intake pipes and rattles pressure switches. The furnace itself may be fine, but its support system takes the hit.</p> <p> I’ve seen brand-new equipment go down because a five-dollar float switch cut power after a wet floor drain backed up. I’ve also seen a 20-year-old unit ride out a lightning storm, only to stop firing because a PVC intake had a bird’s nest washed deeper into it. Storm issues rarely follow neat rules. That’s why the checklist starts broad.</p> <h2> Start with safety, then the thermostat</h2> <p> Treat every post-storm no-heat call as a potential safety issue. If the furnace is in a <a href="https://charlie-wiki.win/index.php/Replacing_vs._Repairing_at_the_End_of_HVAC_System_Lifespan:_A_Guide">local hvac repair services</a> space that took on water, do not power it up. Water and electronics mix poorly, and burners or blower motors that were submerged can short or bind. If the room is dry and there’s no gas odor, you can proceed.</p> <p> Walk to the thermostat and confirm it’s calling for heat. More than once, a battery ran down just enough during an outage to scramble the display. If the screen is blank or flickering, replace batteries if it uses them. If it’s a smart stat, check that it rebooted cleanly and is connected to its base. Some models revert to default settings after a power event, switching from heat to cool or fan-only. Set mode to Heat, raise the setpoint well above the room temperature by 3 to 5 degrees, and set the fan to Auto. Give it a quiet minute to see if anything starts.</p> <p> If the thermostat is fine but the furnace stays still, confirm the date and time on smart stats. I’ve seen schedules misalign after a long outage, pushing the household into “away” mode with a low setpoint that looks like a failure. If your thermostat shows a specific error like “no power to Rc” or “low voltage detected,” that points to a control circuit problem farther down the line.</p> <h2> Power supply and breakers, including the hidden ones</h2> <p> Even gas furnaces depend on steady electricity for the control board, igniter, inducer, and blower motor. Storms can trip a breaker without making a scene. Go to the electrical panel and find the furnace breaker, typically 15 to 20 amps. Don’t just glance at it. Turn it fully off, then back on to reset it. Some panels use older breakers that look “in” even when tripped.</p> <p> Most furnaces also have a local service switch that looks like a light switch. It often sits on or near the side of the unit. In crawlspaces or basements, people bump it while moving storage bins. Confirm that switch is on.</p> <p> Surge damage isn’t always dramatic. I carry a non-contact voltage tester and a small multimeter for a reason. If you’re comfortable, you can open the blower compartment and look for the control board’s status light. No light usually means no power arriving at the board, which points to a tripped fuse on the board or an upstream switch. If the board flashes a code, don’t ignore it. The legend on the furnace door translates those blinks into specific conditions. Two quick blinks might mean pressure switch open, steady light might indicate normal power with no call for heat, and a long-fast pattern could be limit switch open. Each code narrows the hunt.</p> <h2> Post-storm drain and condensate problems</h2> <p> Heavy rain often exposes weak spots in drainage and condensate lines. High-efficiency furnaces produce water during normal operation. They route it through a trap to a drain or condensate pump. If a storm floods a floor drain or kinks a vinyl tube, that water backs up. Safety switches open to protect the furnace, and no heat follows.</p> <p> I see three common scenarios after storms. First, the condensate pump hums but doesn’t pump because its outlet hose is pushed underwater in a floor drain. Pull the hose above the water line so it can discharge. Second, debris in the trap stops flow. You can remove the trap on many units by loosening a couple of clamps. Rinse it in a sink and reassemble, minding the orientation of any check valves. Third, the float switch has tripped. This small device sits in the pump reservoir or on a condensate pan. If it’s up, it’s telling the furnace to stop. Reset the condition by clearing the water and ensuring the pump cycles when you pour in a cup or two.</p> <p> Condensate lines can freeze as well. If a cold snap follows a storm, the trap or the run along a foundation wall may ice up. Thawing can be as simple as warming the space and insulating the line later to prevent a repeat.</p> <h2> Combustion air and venting after wind and snow</h2> <p> Direct-vent furnaces pull combustion air from outside and exhaust through PVC pipes. Wind-driven snow, drifting leaves, and even plastic bags get sucked against intake grilles. I’ve crawled behind shrubs to find intakes caked with wet snow that looks harmless but chokes flow enough to keep the pressure switch from closing. Clear both intake and exhaust terminations. They may be side by side or on different sides of the home. Clear at least a foot around them and look down the pipe with a flashlight. If the pipe is low to grade, check that it hasn’t dipped or pooled water.</p> <p> Some homes rely on combustion air from the room. After storms, people close basement vents or lean plywood against the furnace during cleanup. That can starve the burner. Keep clearance around the furnace as the installation manual describes, usually a couple of feet for service access and air supply.</p> <p> If you have a high-efficiency unit, listen for the inducer motor when there’s a call for heat. It should start first. If it hums but won’t spin, water in the inducer housing or a blocked pressure tube can stop it. If it spins and the board still reports a pressure fault, suspect a blockage farther down the vent or a wet pressure switch hose. Remove the small silicone tube from the switch and check for water droplets. Shake them out, reconnect, and try again.</p> <h2> Gas supply, valves, and pilot systems</h2> <p> Storms can disturb utility supply or inadvertently close valves if someone turned things off as a precaution. Follow the gas line to the furnace. Manual shutoff valves should be parallel to the pipe for open. If it’s perpendicular, it’s closed. Some older homes use sediment traps that can collect water if rain entered an outdoor meter set. That’s rare but it happens.</p> <p> Modern furnaces use hot surface igniters or spark ignition. Standing pilots are uncommon, but if you have one and the wind blew it out through a drafty flue, relighting may restore heat. Follow the exact lighting instructions on the furnace door. If the pilot won’t stay lit, the thermocouple may be loose or failing, or the draft is still excessive.</p> <p> A hot surface igniter glows orange. If you see no glow after the inducer starts, the board may not be powering the igniter, the igniter may be cracked, or a rollout or limit switch is open. You can sometimes spot a hairline crack in the igniter with a close look. Treat these parts gently. Oils from fingers can shorten their life.</p> <h2> Filters, airflow, and the domino effect</h2> <p> Storms drive dust and debris into garages and basements. Filters clog quickly when people run the fan constantly to air things out. A severely restricted filter can open the high-limit switch as the heat exchanger overheats, which the board sees as a safety event. Many furnaces will run the blower and refuse to refire until the limit cools. Replace the filter with a like-for-like size and type. If you upgraded to a very restrictive filter recently, consider stepping down a notch in MERV during heavy heating to preserve airflow unless the system was designed for high static.</p><p> <iframe  src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d3163.3723658700796!2d-84.5519346!3d37.930854800000006!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x88425991f2c8d667%3A0xd6a4fcd021fabe26!2sAirPro%20Heating%20%26%20Cooling!5e1!3m2!1sen!2sph!4v1767010042088!5m2!1sen!2sph" width="560" height="315" style="border: none;" allowfullscreen="" ></iframe></p> <p> I’ve answered no-heat calls where the only issue was a new 1-inch filter with a MERV rating of 13 installed before a blizzard. The blower complained, the furnace shut down mid-cycle, and the code pointed to a limit trip. Restoring a reasonable filter solved the problem. Airflow is not a guess. It’s a measured part of a healthy system.</p> <h2> Resetting safely without making things worse</h2> <p> Boards and safety devices have memories and lockouts. Rapid cycling of power can push a furnace into a hard lockout. If you’ve tried a few things, give the unit a clean reset. Turn off the furnace at the service switch or breaker, wait a full 60 seconds, then restore power. Some models need 3 to 5 minutes after power returns to clear their internal timers and retry the ignition sequence. Be patient. Watch and listen. A normal sequence is call for heat, inducer starts, pressure switch proves, igniter glows or sparks, gas valve opens, flame proves, main blower starts after a short delay.</p> <p> If you get to the ignition stage and the burners light then drop out after a few seconds, that’s a flame sensing issue. Post-storm moisture or a light coating of soot on the flame sensor rod interrupts the tiny microamp signal back to the board. Removing the sensor and cleaning it with a soft abrasive pad can restore the signal. Do not sand it aggressively. You’re polishing, not shaping. Reinstall, ensuring the wire connection is snug.</p> <h2> Flooded equipment: draw the line early</h2> <p> If the furnace sat in standing water, the right move is to shut off power and gas and call a professional. Motors, control boards, gas valves, and safeties are not designed to be submerged. I’ve replaced many assemblies after floods, and while some components dry out and work for a while, their long-term reliability is compromised. Insurance often covers flood-related furnace damage. A proper inspection includes megger testing motors, checking bearings, and verifying that the heat exchanger did not take on water and corrode at seams. Don’t gamble with combustion safety after a flood.</p> <h2> What the system is telling you: symptoms that point the way</h2> <p> Patterns matter. A furnace that runs the blower only, with no attempt to ignite, typically signals an open limit or control issue. A furnace that tries to start multiple times with a “whoomp” followed by shutdown often has venting or flame sensing trouble. Total silence with a live thermostat suggests power is missing at the unit. A faint mechanical hum when the call begins points to a stuck inducer or blower capacitor failure, sometimes caused by a surge.</p> <p> If your home also relies on a central air conditioner and you noticed ac not cooling during the summer after storms, remember that the indoor furnace or air handler serves both. Electrical damage in the control circuit can show up in both seasons. Keeping a simple maintenance log helps spot these relationships. A short note like “breaker tripped twice during July storms” can steer troubleshooting months later when the heater not working seems unrelated.</p> <h2> When to stop and call a pro</h2> <p> You can handle the basics. You should not bypass safety switches, jump pressure switches, or open gas trains without training and test equipment. Call for help if you smell gas, <a href="https://super-wiki.win/index.php/How_to_Increase_HVAC_System_Lifespan_Without_Breaking_the_Bank">fix furnace not heating</a> see scorched wiring, hear arcing, or find water in electrical compartments. Call if your board flashes codes that persist after simple corrections, such as a limit code that returns with a clean filter and open vents. If your furnace is short cycling rapidly, getting hot quickly, and shutting down, don’t keep resetting it. That behavior can point to a blocked exchanger or fan failure.</p> <p> I’ll add a seasonal note. If a big storm exposed weaknesses, schedule a full inspection when the weather stabilizes. That visit should include combustion analysis, static pressure measurement, and verification that safeties and drains are working. Real numbers beat guesswork.</p> <h2> The quiet maintenance that prevents storm fallout</h2> <p> People ask about hvac system lifespan, and storms are part of the story. Most modern furnaces last 15 to 20 years. I’ve seen well-maintained units reach past 25, and I’ve replaced poorly installed ones in under 10. Good drainage, clean power, and clear vents add years. So does realistic filtration. Installing a surge protector at the furnace and at the main panel is cheap insurance. Extending PVC vent terminations a few inches higher, adding intake screens designed for the purpose, and correcting low points in piping prevents water traps that only show up during weather events.</p> <p> For homes with recurring basement water, elevate the furnace on a proper stand and relocate or protect the condensate pump. Tie the pump discharge into a rigid line with an air gap to prevent backflow when drains back up. If you have a smart thermostat, back up its settings or at least know how to reenter Wi-Fi credentials and schedules after an outage.</p> <h2> A disciplined walkthrough you can use every time</h2> <p> Here is a compact checklist that mirrors how I approach a furnace not heating after bad weather. Move step by step, and give the system time to respond between actions.</p> <ul>  <li> Verify thermostat mode, setpoint, and batteries; raise setpoint and wait a minute for a response.</li> <li> Reset the furnace power at the breaker and local switch; confirm the control board status light and note any code.</li> <li> Clear outdoor intake and exhaust terminations; check for snow, leaves, or water in PVC, and inspect pressure switch tubing for moisture.</li> <li> Inspect and clear condensate lines and pump; empty the reservoir, test the pump, clean the trap, and reset any float switch.</li> <li> Replace a dirty filter, open supply and return vents, and ensure the furnace area has adequate combustion air.</li> </ul> <p> If the system still refuses to heat after those steps, you’ve ruled out the common, safe fixes. Take note of board codes and any behavior during startup, then contact a technician with that information. It will speed the diagnosis.</p> <h2> A few real-world edge cases worth knowing</h2> <p> Storms sometimes knock out neutral connections in a home’s electrical system. The result can be weird voltage at the furnace, enough to light LEDs but not enough for motors to start cleanly. If lights in the house brighten and dim or smart devices behave erratically, call an electrician before pushing the furnace any harder.</p> <p> I’ve also seen carbon monoxide detectors shut down furnaces indirectly. After a storm, people move portable generators closer to the house, which trips CO alarms. Some security systems link the alarm to HVAC relays that cut power to the furnace as part of a safety routine. If your CO alarm is chirping or recently alarmed, address that first. Never defeat those interlocks.</p> <p> On sealed-combustion units, water can collect in the collector box at the base of the heat exchanger if a vent becomes partially blocked. The furnace may ignite and then fail on pressure or flame sense once water sloshes. The fix is clearing the vent and draining the collector, a job better left to a pro, but recognizing the symptom avoids chasing the wrong part.</p> <p> Finally, humidity matters. After a rainstorm, the air inside ductwork can be damp, and flame sensors act up. I’ve restored more than one system by cleaning the sensor and letting the furnace run on fan-only for twenty minutes to move dry air through the cabinet before calling for heat again. It’s not magic, just moisture.</p> <h2> Planning forward after you restore heat</h2> <p> When the burners finally stay on and the house warms, the job isn’t finished. A short post-mortem prevents repeat problems. Note what you found and fix the root cause. If snow blocked a low intake, extend it or clear a path before the next storm. If the breaker tripped, consider adding a furnace-specific surge protector or talking to an electrician about the panel. If the condensate pump stuck, replace it before it fails on a holiday morning. A $60 pump is cheaper than a service call and far cheaper than a flooded floor.</p> <p> Tie this experience into your broader system care. The same habits that keep the furnace steady will help the cooling side. If you’ve fought ac not cooling during storm season because of clogged outdoor coils and debris, think of seasonal cleanup as a single routine. Clear the outdoor unit in spring and the intake and exhaust in fall. Mark filter changes on a calendar. If your heater not working scare led you to discover an old thermostat or brittle wiring, upgrade on your schedule rather than during the next emergency.</p> <h2> The bottom line from the field</h2> <p> Storms expose weak links. Most of the time, the furnace is doing exactly what it should when it refuses to run after bad weather. Safety circuits detect water, blocked vents, missing airflow, or confused controls, and they hold the line. Respect those signals. Work through the simple checks, and you’ll often find a small fix that restores heat without drama. When the signs point beyond that, bring in a qualified tech. They’ll confirm safe operation, check combustion numbers, and make sure your hvac system lifespan isn’t quietly shortened by a storm you thought you survived.</p> <p> The best systems I service aren’t the fanciest. They’re the ones with clear air paths, dry floors, tidy wiring, and owners who listen to their equipment and write down what they see. That’s how you turn a storm from a blackout story into a footnote.</p><p> </p><p>AirPro Heating & Cooling
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Address: 102 Park Central Ct, Nicholasville, KY 40356
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Phone: (859) 549-7341
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