Blower motor loss of rotor control or high current trip

What is going on

This fault means the circulator blower motor lost track of its rotor, or it saw a surge of current, and the control shut the furnace down. In plain words, the motor was suddenly working a lot harder than it should. Think about anything that could jam it or choke its air. Dirty filters, blocked registers and something stuck in the blower wheel are all common, so check those before you condemn the motor. Power off first, because that wheel can start without warning.

Likely causes

• Abnormal motor loading
• Sudden change in speed or torque
• Sudden blockage of furnace air inlet or outlet
• Debris or a loose wheel rubbing in the housing

Check in this order

1. Turn power off before repair
2. Check filters, filter grills, registers, duct system and furnace air inlet and outlet for blockages
3. Check the circulator blower for obstructions. Remove and repair or replace the wheel or motor if needed
4. Spin the wheel by hand and feel for drag or noise in the bearings
5. Replace the motor or wheel with the correct replacement part if needed
6. Restore power and watch a full cycle for a repeat fault

More furnace guides

• Airflow lower than demanded, furnace runs on low stage when high stage is expected
• Alternate combustion air opening (upflow or horizontal)
• Alternate vent/flue location (upflow or horizontal left)
• Annual inspection checklist
• Auxiliary limit control (location and purpose)
• Auxiliary limit switch open (blower compartment)