What happens
The motor or its supported electronics cannot drive the blower.
Typical symptoms
Outdoor unit runs with little or no indoor airflow; the indoor coil may freeze.
Checks that distinguish this cause
Stop cooling if airflow is absent. Verify required supply, command, wiring and mechanical freedom with the OEM procedure, separating PSC capacitor tests from ECM electronics diagnostics.
What can look similar
A missing G signal, open relay or failed power connection can stop an intact motor.
Repair direction
Replace the confirmed approved motor or drive and investigate abnormal loading.
Verify the repair
Verify commanded airflow and safe cooling operation after all ice has thawed.
Equipment-specific limits
Airflow depends on the wheel, duct pressure and configuration as well as motor rotation. Match the procedure to PSC, constant-torque ECM or variable-speed ECM technology.
Practice this diagnosis
These simulated calls exercise this component or repair family. The article describes a broader diagnostic process; a call may represent a different cause within that family.
References and applicability
Original HVACSim explanations with manufacturer and instrument-maker references for further reading. These resources support the subject; their model-specific examples are not specifications for every system.
- Copeland: CoreSense diagnostics for scroll air-conditioning compressors (AE8-1379)Model-specific diagnostic examples; flash codes are not universal.
- Carrier: HVAC installation and commissioning overviewSizing, airflow, charge and A2L installation considerations; obtain the exact unit manual.
Editorial review: 2026-09-29. Verify the current manual for the installed model.