How to test a blower motor when HVAC furnace displays a "blower cannot run" code

Introduction

This tutorial provides a step-by-step guide on how to test a blower motor when your HVAC furnace displays a "blower cannot run" error code, specifically error code 61. This process can help identify if the blower motor is faulty without needing specialized testing equipment. Always remember to exercise caution when working with electricity.

Step 1: Verify the Error Code

• Check the furnace display for error code 61, which indicates an issue with the blower motor.
• Understand that potential causes may include:
  • Bad motor
  • Wiring issues
  • Mechanical failure
  • Faulty electronic control module (ECM)
  • Power factor choke (PFC) issues
  • Corrupted furnace data

Step 2: Test the Furnace Operation

• Cooling Mode Test:

  • Set the thermostat temperature below room temperature to call for cooling.
  • Reset the code by turning off the furnace disconnect.
  • Restore power and check if the AC compressor starts and if the furnace operates.
  • If the furnace does not start or stops shortly after, the error code will reappear.

• Heating Mode Test:

  • Set the thermostat temperature above room temperature to call for heating.
  • Repeat the code reset by turning off the furnace disconnect and restoring power.
  • Check if the induced draft motor activates and if the blower starts.
  • Again, if the furnace fails to start or stops after a brief period, the error code will show.

Step 3: Access the Blower Motor

• Turn off the furnace completely.
• Open the blower compartment to access the blower motor.
• Inspect the wiring for:
  • Loose connections
  • Damage or wear

Step 4: Test the Blower Motor Directly

• Prepare for the test using two pieces of 12-gauge solid copper wire, stripped on both ends.

• Disconnect the motor control wiring plug from the furnace control board (P5).

• Identify the following pins on the plug:

  • Pins 3 and 4 (orange and brown wires for 24 volts)

• Connect the prepared wires:

  • Insert one end of each wire into pins 3 and 4.
  • Disconnect the 24-volt transformer wires from the control board and connect them to the other ends of the prepared wires.

• Power On:

  • Turn on the disconnect switch.
  • Press the door switch or close the blower compartment door.

• Observe the blower motor:

  • If operational, it should start and run at full speed.
  • If it does not start, or starts and stops shortly, the motor is likely faulty.
  • If it runs at reduced speed, the ECM may be defective and require replacement.

Step 5: Reconnect and Finalize

• After testing, turn off the disconnect switch.
• Reconnect the transformer wires and the motor control cable to the furnace control board.
• If the blower motor is confirmed faulty, plan to replace it.

Conclusion

Testing your blower motor can help diagnose issues with your HVAC system effectively. By following these steps, you can determine if the motor is the source of the problem and take appropriate action. Always prioritize safety, and if you are unsure or uncomfortable with these procedures, consider contacting a professional.