A furnace usually gives hints before it completely fails. Strange noises, short cycling, or uneven room temperatures often show up weeks ahead of equipment shutting down. Knowing the most common causes of HVAC failures helps you act before a small issue becomes an expensive repair or replacement. At Affordable Service Solutions Heating & Air Conditioning, in Richmond, KY, we help homeowners spot issues early and fix them the right way. Read on to understand why furnaces fail and how timely, professional service keeps your home reliably comfortable.
1. A Dirty or Restrictive Air Filter
Air must move freely across the heat exchanger for your HVAC system to work properly. A clogged filter impedes airflow, raises internal temperature, and can cause damage to internal components. You may notice short run cycles, weak airflow in distant rooms, or a hotter-than-normal furnace cabinet. A technician can check static pressure and confirm you’re using the proper filter size and rating.
2. Ignition or Pilot Light Problems
Older units use pilot lights, while newer models rely on hot surface igniters or spark ignition. A weak pilot light, cracked igniter, or misaligned spark causes failed starts and repeated clicking. Sometimes the gas valve opens, but the flame does not carry across the burners. A professional tests voltage to the igniter, inspects flame travel, cleans burner faces, and replaces parts that no longer light cleanly. Stable ignition protects the heat exchanger and keeps the cycles smooth.
3. Flame Sensor Contamination
The flame sensor tells the control board that gas is burning. When the rod is coated with oxides, the board reads no flame and shuts the valve. That leads to rapid start and stop behavior. Technicians measure microamps while the unit runs, clean or replace the sensor, and verify an even flame across the rack. With confirmation of a proper signal, the furnace stops dropping out mid-cycle.
4. Blower Motor or Capacitor Failure
If the blower cannot move air, heat accumulates and safety features may engage. You might hear a hum with no airflow or feel the burner start while the rooms never warm. Common causes include worn bearings, a failed run capacitor, a dirty wheel, or a control board that is not sending a solid call. Testing covers amperage draw, capacitor value, wheel balance, and wiring at the motor and board. Correcting the fault restores stable airflow and temperature rise.
5. High Limit Trips and Overheating
The high limit switch protects the furnace from excessive heat. Frequent trips point to low airflow, blocked returns, dirty indoor coils on downflow setups, or gas input that needs adjustment. A professional measures the temperature rise, compares it to the rating plate, and then fixes the root cause. That may involve duct repairs, return upgrades, or adjusting manifold pressure with a manometer.
6. Cracked Heat Exchanger
Metal expands and contracts with each cycle. With age and repeated overheating, the heat exchanger can crack. Warning signs include flame movement when the blower starts, bad odors, or a carbon monoxide alarm sounding. This is a safety concern that calls for immediate evaluation. Professionals use lights, mirrors, or cameras, and combustion testing to confirm a failure. When a crack is verified, replacement is the safe path because gas and air must stay separated during operation.
7. Venting or Condensate Problems
High-efficiency furnaces produce water, which moves away from your unit through a drain line. A damaged hose or mineral deposits can block flow. You may notice water pooling near your unit. Your system may turn off if safety features are engaged to prevent water damage.
Standard furnaces depend on intact metal flues and a steady draft. Leaves, nests, or loose joints interrupt venting and shut the system down. A licensed technician clears lines, restores proper slope, checks draft at the test port, and validates pressure switch operation so the furnace can run safely.
Keep Heat Steady With the Right Team
Homeowners want to reap the benefits of reliable use of their HVAC system, lower risk of surprise outages, and honest guidance when repair or replacement is necessary. Our team at Affordable Service Solutions Heating & Air Conditioning provides prompt diagnostics, seasonal maintenance, fast repairs, and correctly sized furnace installations. This is in addition to other related services like thermostat installation and airflow balancing to support safe, steady heating. Book your furnace service with Affordable Service Solutions Heating & Air Conditioning today and keep your Richmond home warm when it matters most.
