It’s a frigid winter night when suddenly your furnace stops producing heat, leaving your home freezing. Few scenarios strike dread into homeowners more than a faulty furnace. But many common furnace malfunctions stemming from routine wear and tear can often be identified and resolved fairly easily.
Understanding the typical failure points and how to troubleshoot them yourself can save you money on repairs. Here are some of the most common furnace problems along with steps to try getting the heat flowing again:
Furnace Won't Ignite
If the furnace isn’t firing up at all when you call for heat, the problem may be a simple pilot light outage. Try relighting the pilot following the manufacturer’s instructions. Locate the small pilot access panel, press the igniter button, and let the pilot ignite. If the pilot won’t stay lit, its sensor may need replacement by a pro.
For furnaces with spark ignition, no fire means the igniter could be malfunctioning. Swap the hot surface igniter out if cracked or worn. Check that the furnace is getting voltage and the igniter is heating up. No gas flow points to a problem with the gas valve requiring service.
Heat Runs Continuously
Lack of temperature control is often traced back to the thermostat. Try turning it off for 30 seconds and rebooting it to reset the device. Verify your desired temp is programmed correctly. If adjusting the thermostat settings doesn’t stop continuous heating, issues with the control board or a stuck relay may be to blame.
Noisy Operation
Loud rumbling, squeaking, grinding or thumping sounds indicate a problem. Belt noise means pulleys may need lubrication or realignment. Screeching flow noises point to blower damage. And grinding sounds signal worn out motor bearings needing replacement. Have the specific sound diagnosed by an HVAC pro.
Burning Smells
Odd odors like burning plastic or sulfur coming from the furnace could signify overheated electrical components, a cracked heat exchanger leaking exhaust, or a gas leak. Shut off the gas valve and power until a technician can inspect for the smell’s origin. Don’t run a malfunctioning furnace producing strange smells.
Short Cycling On and Off
If your furnace keeps kicking on for a few minutes then shutting back down, a problem is interrupting normal operation. Dirty filters, closed vents, loose wiring, or flame sensor issues can all cause short cycling that strains the furnace. Check for simple airflow obstructions first before calling for repairs.
Not Producing Enough Heat
There are several possible causes of inadequate heat: dirty filters and restricted airflow; blower fan problems reducing air delivery; or a clogged heat exchanger unable to transfer warmth. Have an HVAC tech evaluate temperature output and airflow to pinpoint insufficient heating causes.
Slow or Delayed Startup
If the furnace doesn’t immediately fire up when you call for heat, the flame sensor may need cleaning so it recognizes the pilot is lit. Slow ignition can also mean problems with the thermocouple telling the gas valve to open and let fuel through. An inspection can identify the lag cause.
Flame Burning Too Low
Lazy orange flames instead of vibrant blue and too much black smoke indicate combustion issues. A low flame can result from insufficient air intake. Or the gas valve may need adjustments to improve fuel mix and flame quality. Left alone, sooty flames lead to dangerous buildup and efficiency loss.
Rattling Noises
If the furnace ducts vibrate, rattle or resonate, airflow is likely hitting obstructions. Dents in ductwork, closed vents and excess lint buildup can all create turbulence. Removing blockages and sealing up gaps smooths out airflow and reduces noise. Properly sizing ducts to the furnace prevents velocity noise.
Frost Forming on Vents
Frost accumulating on air registers and cold air returns points to a dangerous crack in the heat exchanger leaking indoor air. This allows warm interior air to mix with exhaust gasses, creating condensation. Has the heat exchanger fully inspected and tested for leaks? Repairs are crucial to prevent carbon monoxide.
While troubleshooting furnace problems yourself can save money if done safely, know your limits. Some codes require certified HVAC technicians conduct repairs. But trying a few easy fixes yourself can get heat flowing again and avoid late night service calls. Just don’t let problems linger - get all furnace issues properly diagnosed and resolved before the deep cold hits. Stay warm!