What Causes a Heater Fan to Stop Working?

What to do When the Furnace Fan Stops Working?

As temperatures fluctuate, having a reliable HVAC system is crucial for maintaining a comfortable home environment. A common issue that can disrupt this comfort is a blower fan refusing to start. Whether you’re dealing with a furnace, air conditioner (AC), or heat pump, understanding the potential culprits behind a non-starting blower fan is essential. In this guide, we’ll explore the ten most common reasons for this problem.

  1. Capacitor Issues: 
  • PSC (Permanent Split Capacitor) blower fans require a capacitor for both starting and running the motor. A faulty capacitor can disrupt the artificial phase of electricity needed for the blower motor’s power supply.
  • Testing the capacitor: Use a multimeter to check the MFD (microfarads) reading. If it deviates more than 6% from the rating on the capacitor, it’s likely defective.
  1. Blower Motor Damage:
  • After replacing a bad capacitor, the blower motor may exhibit intermittent operation and a burning smell, indicating damage sustained during the capacitor’s malfunction.
  • Note: Always be prepared to replace the blower motor when dealing with a bad capacitor.
  1. Blower Motor Electrical Windings:
  • If the motor windings have opened up, shorted, or grounded, the motor won’t start. Use a multimeter to check resistance values between wires, ensuring the motor is cool before testing.
  • Tip: A 120v PSC blower motor example illustrates different resistance values for various speed wires.
  1. Blower Motor Bearings: Check for easy turning and the absence of wiggling. Difficulties in spinning or wiggling may indicate a bad bearing.
  2. ECM Blower Motor Module:
  • Electronically Commutated Motors (ECM) may have a faulty module preventing the motor from turning on. Use a multimeter to check for high-voltage power to the motor.
  • Note: Inspect the module visually for any signs of damage or burning.
  1. Bad Control Board:
  • For units with ECM motors, a malfunctioning control board may fail to communicate with the blower motor. Test the motor with a TecMate PRO to eliminate the issue.
  • Tip: Check for loose wiring and ensure the motor receives a 24v signal from the G to C terminals.
  1. Thermostat Face: A drained battery in the thermostat or lack of a common wire can prevent the blower motor from starting. Replace batteries regularly and bypass the thermostat for testing.
  2. Power Off to the Furnace or Air Handler: Ensure the power switch is on, the door switch is engaged, and check for error codes on units with LED displays.
  3. Thermostat Wiring:Damaged thermostat wiring can be the culprit. Check for issues such as animal damage or wire compression during installation. Tip: Bypass the thermostat for testing by jumping from R to G at the control board.
  1. Ductwork Issues: Clogs or collapses in the ductwork can impede airflow, even if the blower motor is operational.

What is a furnace inducer motor?

A furnace inducer motor is a component in a gas furnace that helps initiate combustion, removes combustion byproducts, and ensures proper ventilation. It plays a key role in the efficiency and safety of the furnace by creating the necessary airflow for combustion and venting.

How to replace a furnace blower motor?

Replacing a furnace blower motor involves turning off the power, disconnecting wires from the old motor, removing the old motor, installing the new motor, connecting wires, testing the new motor, and securing panels. If you’re not experienced, it’s safer to hire a professional for this task.

How do you know if your blower motor is bad?

A faulty blower motor in your HVAC system can manifest through various signs. Here are common indicators that your blower motor might be bad:

  1. No Airflow: If you notice little to no airflow coming from your vents, it could indicate a blower motor problem. The motor is responsible for circulating air through the system, and a malfunction can lead to reduced or no airflow.
  2. Weak Airflow: Weak or significantly reduced airflow, even when the system is running, can suggest a struggling blower motor. This might be due to a decrease in the motor’s efficiency.
  3. Unusual Noises: Strange noises, such as squealing, grinding, or rattling, when the HVAC system is running could indicate issues with the blower motor. These sounds may suggest worn-out or damaged components within the motor.
  4. Intermittent Operation: If the blower motor operates inconsistently, turning on and off unexpectedly, it might be a sign of a malfunction. This behavior can lead to uneven heating or cooling in your home.
  5. Overheating Smell: A burnt or overheating smell coming from your vents could indicate a blower motor problem. If the motor is working too hard or experiencing electrical issues, it may produce a noticeable odor.
  6. Motor Won’t Start: If the blower motor fails to start altogether, it’s a clear sign of a problem. This could be due to issues with the motor itself, the capacitor, or other electrical components.
  7. Increased Energy Bills: A malfunctioning blower motor may cause your HVAC system to work harder to maintain the desired temperature. This increased workload can lead to higher energy bills.
  8. Visible Damage: If you can visually inspect the blower motor, look for signs of physical damage, excessive dirt or debris, or signs of overheating, such as discoloration.

Attempting to repair or replace a blower motor without the necessary expertise can lead to further damage or safety hazards. A professional technician can accurately identify the issue and recommend the appropriate course of action, whether it involves repairing or replacing the blower motor.

Why my furnace won’t shut off even when the thermostat is off?

If your furnace continues to run even when the thermostat is set to the “off” position, several potential issues may be causing this problem. Here are some common reasons:

  1. Thermostat Malfunction: The thermostat might be faulty or incorrectly wired. Check if the thermostat is set to the “off” position, and if it is, examine the wiring to ensure proper connections. If the thermostat is still causing issues, it may need to be replaced.
  2. Shorted Wires: Short circuits in the thermostat wires or in the furnace control board can keep the furnace running. Inspect the thermostat wires for any signs of damage, and check the control board for shorts.
  3. Stuck Relay or Contact: The relay or contact switch in the furnace control board may be stuck in the closed position, keeping power flowing to the furnace even when it should be off. This issue often requires professional attention to diagnose and fix.
  4. Faulty Limit Switch: The limit switch is a safety feature that turns off the furnace when the temperature inside the furnace becomes too high. A malfunctioning limit switch may fail to shut off the furnace when needed.
  5. Dirty or Clogged Air Filter: A clogged air filter can cause the furnace to overheat, triggering the limit switch to shut down the burners but not the blower. Ensure that the air filter is clean and replace it if necessary.
  6. Issues with the Thermostat Wiring: Check for loose or improperly connected wires in the thermostat wiring. If there are issues with the wiring, the thermostat may not be effectively communicating with the furnace.
  7. Faulty Thermostat: If the thermostat is not sending the signal to the furnace to shut off, it could be malfunctioning. Consider replacing the thermostat if other troubleshooting steps do not resolve the issue.
  8. High Thermostat Setting: Ensure that the thermostat is not set to an unusually high temperature, causing the furnace to continue running to reach the set temperature.

Working with heating systems involves dealing with electrical components, and professional expertise is crucial to ensure safety and proper diagnosis of the problem.


A blower fan refusing to start can stem from various issues, each requiring a specific approach for resolution. Regular maintenance and timely troubleshooting are crucial for keeping your HVAC system running smoothly. If you encounter difficulties or are unsure about addressing these problems, it’s wise to consult a professional technician.

At Heald Mechanical, we prioritize your comfort and peace of mind. Our experienced technicians specialize in diagnosing and resolving HVAC issues promptly. Contact Heald Mechanical for reliable services that ensure your HVAC system operates at its best, providing you with comfort year-round.

Frequently Asked Questions

What to do when a furnace stops working?

  • Check the thermostat settings and ensure it’s in heating mode.
  • Verify the power supply by checking the circuit breaker.
  • Inspect the air filter for clogs and replace if necessary. If issues persist, seek professional HVAC assistance.

What to do when your heater is not working?

  • Confirm the thermostat is set to the desired temperature and heating mode.
  • Check the power supply, reset the circuit breaker if needed.
  • Inspect the air filter for blockages and, if the problem persists, contact a heating professional for further diagnosis.

What happens when the furnace capacitor goes bad?

  • A failing furnace capacitor can result in reduced motor functionality.
  • This may lead to issues with the blower motor starting or running smoothly.
  • Consult an HVAC professional for capacitor replacement and a comprehensive system assessment.

What to do when your furnace stops working?

  • Check thermostat settings and ensure it’s set to the desired temperature.
  • Verify the power supply by checking the circuit breaker.
  • Inspect the air filter for clogs, and if the problem persists, contact an HVAC professional for expert assistance.

What to do when the furnace won’t turn on?

  • Ensure the thermostat is set to the heating mode and the desired temperature.
  • Check the circuit breaker for a tripped switch and reset if necessary.
  • If the furnace still won’t turn on, seek assistance from an HVAC professional to diagnose and address the issue.