When this is an emergency
Stop troubleshooting and get help immediately if any of these are happening:
- Carbon monoxide (CO) alarm sounds — get everyone outside into fresh air and call 911.
- You smell gas (often described as a “rotten egg” odor) — leave immediately and call your gas utility and/or 911 from a safe location.
- Smoke, sparks, or an electrical burning smell — shut the system off only if it’s safe, then call for help.
- Anyone feels dizzy, nauseated, confused, unusually tired, or has a severe headache — get fresh air and seek medical help.
Safety note: CO is odorless and dangerous. If your alarm sounds, treat it as real. For official safety guidance, review the CDC carbon monoxide safety recommendations.
Quick no-heat checklist (safe homeowner checks)
- Thermostat: Set to HEAT, temperature above room temp, and fan to AUTO. Replace batteries if it has them.
- Power: Check the breaker and the furnace service switch (often looks like a light switch near the unit).
- Filter: If the filter is clogged, replace it. Restricted airflow can trigger safety shutoffs.
- Vents: Confirm supply and return vents are open and not blocked by rugs/furniture.
- High-efficiency exhaust/intake: If you have PVC pipes outside, make sure snow/ice/debris isn’t blocking them.
If the breaker keeps tripping: stop resetting it and schedule service.
Eight common furnace problems in winter (and what to do)
Clogged air filter reduces airflow and heat
A clogged filter can restrict airflow so badly that the furnace overheats and shuts down for safety.
Safe check: Replace the filter and restart the system. If it keeps shutting down, schedule service.
Thermostat malfunctions or power issues
Sometimes the furnace is fine but the thermostat isn’t calling for heat—or the furnace isn’t receiving power.
Safe check: Verify HEAT mode, replace batteries, confirm breaker and service switch. If power issues repeat, call a professional.
Ignition or pilot problems
Older furnaces may use a standing pilot; newer systems use electronic ignition. Ignition issues can prevent burners from lighting.
Safe check: If you smell gas or the unit repeatedly fails to ignite, stop and call for service. Don’t attempt unsafe DIY ignition work.
Uneven heating and cold rooms
Cold spots can be caused by blocked vents, restricted airflow, duct leaks, or a blower issue.
Safe check: Open vents, remove obstructions, replace the filter. If some rooms still don’t heat, have ducts/blower evaluated.
Short cycling (turns on and off too often)
Short cycling can indicate overheating, airflow restriction, thermostat problems, or sizing/control issues. It increases wear and energy waste.
Safe check: Replace the filter and confirm thermostat settings. If it continues, schedule service before it becomes a bigger failure.
Strange noises (banging, booming, screeching)
Loud or new noises are not “normal.” Booming can indicate delayed ignition; screeching can point to motor/bearing problems.
Safe check: If noises are loud/violent or persistent, shut the system down and call for service.
Unusual smells or carbon monoxide warnings
A brief “dust burn” smell can happen at start-of-season. But electrical burning smells, gas odors, soot, or a CO alarm are serious.
Safe check: If a CO alarm goes off or you smell gas, leave and call emergency services.
Skipped maintenance leads to mid-winter breakdowns
Annual maintenance catches failing parts early and helps confirm safe operation before peak winter demand.
Best practice: Schedule a fall tune-up to reduce no-heat calls during the coldest weeks.
Furnace Not Working? Don’t Guess. Diagnose It Properly.
If your furnace won’t turn on, keeps shutting off, or is blowing cold air, the issue could be ignition failure, a dirty flame sensor, airflow restriction, or a faulty control board. Quick fixes are fine — but misdiagnosing it can cost you more.
EMCO Tech performs full heating diagnostics, checks safety limits, verifies gas pressure, inspects heat exchangers, and restores safe, reliable heat the right way.
Need help now?
If you need a technician, use these service pages:
- Emergency heating repair (no-heat calls, urgent breakdowns)
- Gas furnace repair in Philadelphia
FAQ
If the blower is running but you’re getting cold air, common causes include a dirty filter restricting airflow, a failed ignition component, incorrect thermostat settings, or a burner issue. Try checking the thermostat mode (Heat), replacing the filter, and verifying the system didn’t trip a safety limit. If it keeps happening, the furnace needs proper diagnostics.
Start with the basics: confirm the thermostat is set to Heat and above room temperature, replace thermostat batteries, check the furnace switch is on, and look for a tripped breaker. If you have a condensate safety switch (common on high-efficiency units), a clogged drain can shut the system down too.
Short cycling is often caused by overheating from restricted airflow (dirty filter, blocked vents), a faulty flame sensor, a thermostat problem, or an oversized furnace. It’s hard on the system and can lead to bigger failures. Replace the filter and make sure vents are open, but repeated short cycling should be inspected.
A light burning-dust smell can be normal for the first run of the season and usually fades within a short time. A sharp electrical smell, melting plastic odor, or smoke is not normal. If you smell something strong or unusual, shut the system off and schedule service.
Leave the building immediately and contact your gas utility from a safe location. Do not flip switches, use electronics, or try to restart the furnace. After the utility confirms it’s safe, have an HVAC technician inspect the furnace and gas piping before running the system again.
Yes. A severely clogged filter can restrict airflow enough to trigger the high-limit safety switch, causing the furnace to shut down or short cycle. It can also reduce comfort and increase energy use. Filter replacement is one of the simplest ways to prevent no-heat calls.
Common ignition problems include a dirty flame sensor, a failed hot surface igniter, a weak spark igniter, dirty burners, or issues with the gas valve and control board. Because ignition involves combustion and safety controls, it’s best handled by a licensed technician once basic checks are done.
Treat it as urgent if indoor temperatures are dropping quickly, you have vulnerable occupants (infants, seniors), pipes are at risk of freezing, you smell gas, or you have a carbon monoxide alarm event. If you suspect a safety issue, shut the system off and call for emergency HVAC service.
If you hear loud bangs, booms, grinding, or repeated clicking without ignition, shut the system off and schedule service. Booming can be delayed ignition, which can damage components and create unsafe conditions. Don’t keep cycling it and hoping it sorts itself out.
Most homes benefit from a yearly inspection before winter. A tune-up typically includes cleaning, safety checks, combustion testing (where applicable), and verifying proper operation of ignition and airflow. Preventive maintenance reduces breakdown risk and catches problems early.
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