ECM Blower Diagnosis on a Carrier Infinity System (HVAC Variable Speed Blower Diagnosis)
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The errors were Error 41-Blower Motor Fault and Error 44-Cannot Communicate With Blower. The communications light was on, but the status light was blinking at the control board. Bryan started by restarting the power to see if anything changed. While the power was off, Bryan checked the plugs and blower condition. The plugs seemed to be in good condition, and the blower didn’t appear to be stuck.
After forcing the time delay off using the thermostat, we still saw that the blower wasn’t communicating with the board. The static pressure was a little bit higher than normal because Bryan made the unit run at maximum airflow for a video, but that shouldn’t have been a problem that would have led to the current situation (the static pressure stayed within the normal operation range). Bryan’s main suspicion was that the higher RPM was what led to a failure in the motor module, which made the motor unable to communicate with the blower.
We removed the blower to separate the motor from the module. Bryan confirmed that the motor would run shortly upon startup, but it would fail to communicate and would stop running. There didn’t appear to be any bearing or winding abnormalities when we took it apart. We swapped out the module at Kalos; it had the same horsepower but didn’t have the “3.0” label. On systems with VFDs, be sure to leave it disconnected from high voltage for about 5 minutes for safety reasons.
Having read the windings against each other, we determined that they had roughly the same resistance (which is normal for three-phase motors). After checking them all to ground, we determined that there was no significant resistance.
The new motor module was installed, and the error code went away on the board. There were no error codes at the thermostat, and the blower only drew 2.1 amps. The static pressure was at 0.4″wc, and all was well.