What happens
Mechanical obstruction, incorrect rotation or the wrong blade arrangement limits heat rejection.
Typical symptoms
Weak outdoor airflow, fan noise or elevated operating pressure during cooling.
Checks that distinguish this cause
Inspect isolated blade clearance and installation. Compare rotation and airflow direction with the unit diagram; evaluate guards, debris and nearby recirculation paths.
What can look similar
A dirty coil can restrict heat rejection even with correct fan operation.
Repair direction
Correct the obstruction or approved motor/blade configuration.
Verify the repair
Verify airflow and system performance under a representative cooling load.
Equipment-specific limits
Identify PSC, ECM or other motor technology and rotation requirements. Keep clear of automatic starts and moving blades.
Practice this diagnosis
This cause is a reference topic; it does not yet have a dedicated simulated call. Browse the practice board.
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.
- Fluke: How to measure capacitancePower isolation, discharge and capacitance measurement.
Editorial review: 2026-09-29. Verify the current manual for the installed model.