Loss of communication with circulator blower motor

What is going on

The integrated control module and the circulator motor have stopped talking to each other, and the furnace won't run. What I usually find is a plug that's backed out or a loose control lead, so start there before you condemn the motor. Motor and board both fail occasionally, but wiring comes first.

Likely causes

• Loose wiring at the circulator motor control leads
• Failed circulator blower motor
• Failed integrated control module

Check in this order

1. Turn power off before repair.
2. Reseat and tighten the motor control lead connections and look for pins that are pushed back or corroded.
3. Tighten or correct the wiring connection wherever you find a fault.
4. Check the circulator blower motor and replace it if needed.
5. Check the integrated control module and replace it if needed, once wiring and motor are cleared.
6. Restore power and watch for communication on a call for heat.

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)