When troubleshooting the A/C schematic, if the thermostat contacts are closed, the compressor and condenser fan motor are short cycling, and the blower motor is not running, what is the most likely fault?

When troubleshooting the A/C schematic, if the thermostat contacts are closed, the compressor and condenser fan motor are short cycling, and the blower motor is not running, what is the most likely fault?

• A. A faulty blower motor or blower relay
• B. A faulty thermostat
• C. A shorted compressor
• D. An open high-pressure switch

Answer: (A)

When the thermostat calls for cooling, both the indoor blower and the outdoor compressor/condenser should run smoothly together. If the outdoor unit is short cycling while the indoor blower is not running, the most plausible fault is in the indoor blower circuit itself—either the blower motor or the blower relay on the control board. A failure here stops air from moving across the evaporator, so there’s little heat transfer and the system protection or control logic may cause the outdoor unit to start and stop repeatedly. This single indoor fault explains both the blower being dead and the erratic outdoor cycling. A faulty thermostat wouldn’t typically produce a situation where the call is active (contacts closed) but the blower remains stopped while the outdoor unit cycles; it would more likely affect whether the call is made at all. A shorted compressor would normally result in continuous operation or a clear fault condition rather than intermittent cycling with no indoor airflow. An open high-pressure switch would usually prevent the outdoor unit from starting, not cause it to short cycle while the blower stays off.

When the thermostat calls for cooling, both the indoor blower and the outdoor compressor/condenser should run smoothly together. If the outdoor unit is short cycling while the indoor blower is not running, the most plausible fault is in the indoor blower circuit itself—either the blower motor or the blower relay on the control board. A failure here stops air from moving across the evaporator, so there’s little heat transfer and the system protection or control logic may cause the outdoor unit to start and stop repeatedly. This single indoor fault explains both the blower being dead and the erratic outdoor cycling.

A faulty thermostat wouldn’t typically produce a situation where the call is active (contacts closed) but the blower remains stopped while the outdoor unit cycles; it would more likely affect whether the call is made at all. A shorted compressor would normally result in continuous operation or a clear fault condition rather than intermittent cycling with no indoor airflow. An open high-pressure switch would usually prevent the outdoor unit from starting, not cause it to short cycle while the blower stays off.