HVAC technicians know a home’s heating and cooling system is essential for comfort and safety—especially with winter around the corner. Now’s the time to make sure your furnace and ductwork are ready, so small issues don’t turn into mid-season emergencies.
Common Furnace Problems
Your furnace can be a reliable workhorse for years with the right upkeep. If something’s off, start here. These are the most frequent issues we see (and what to do next).
Lack of Maintenance
This is the #1 reason a heater won’t turn on or won’t heat well. Skipping your seasonal tune-up leads to performance and safety problems.
- Dirty filters: Dust, dander, and debris clog filters even when the heater sits idle. Check and replace before first use each season.
- Dusty burners: Uneven flames = uneven heat, higher fuel use, and more wear. Clean burners before the heating season to keep combustion stable. More on warning signs in our furnace safety guide.
- Dirty blower: A dust-caked blower slows airflow. The heat exchanger relies on airflow to prevent overheating—keep the blower clean to protect the system.
Improper Gas Supply
Your furnace needs gas pressure calibrated to spec. Off-spec supply causes nuisance shutdowns and poor comfort.
- Too much gas: Overheats the furnace, spikes bills, and can trip high-limit safeties.
- Too little gas: Weak heat output, longer run times, and higher energy use as the system struggles to keep up.
Malfunctioning Blower Capacitor
The blower capacitor (a can-shaped component) delivers the electrical boost that starts and runs fan motors. When it weakens or fails, the blower won’t start, and the furnace may lock out. A technician can test and replace it quickly.
Low Refrigerant (Heat Pumps)
If you heat with a heat pump, low refrigerant forces electric heat strips to kick in more often—raising bills and risking compressor damage from overheating. Refrigerant diagnostics and charging are pro-only tasks.
Faulty Starting Components
Relays, contactors, and control boards can stick or fail. Left unresolved, you’ll see:
- Blower won’t start or short-cycles
- No heat even though the thermostat calls for it
- Collateral damage to internal components
Failed Draft Inducer
The draft inducer clears residual combustion gases before ignition. If the motor burns out or seizes, the pressure switch won’t prove draft and the furnace shuts down for safety. Replacement is straightforward but should be done by a licensed tech.
Cracked Heat Exchanger (Serious)
A cracked exchanger may not stop the furnace immediately, but it does compromise safety and efficiency. It can allow combustion byproducts—including carbon monoxide—into your airstream. If you suspect this, shut the system off and call a professional immediately. Learn more warning signs here.
“Before you know it, you’ll be wondering how to lower your electric bill this winter—
but safety comes first.”
Improper or Aging Ductwork
Older homes often have undersized, leaky,_
