Under the same scenario but with the compressor and condenser fan motor not running while the blower motor is running, which components are most likely open?

Under the same scenario but with the compressor and condenser fan motor not running while the blower motor is running, which components are most likely open?

• A. The HP, LP, overloads, and oil pressure switch are open
• B. The thermostat is defective
• C. The blower motor is faulty
• D. The condenser fan is blocked

Answer: (A)

When the indoor blower keeps running but the compressor and condenser fan are not, the outdoor unit is being kept from starting by safety/interlock devices rather than a simple thermostat or motor failure. The high‑pressure switch, low‑pressure switch, motor overloads, and the oil pressure switch are all designed to interrupt power to the compressor and the condenser fan if conditions are unsafe or abnormal. If any of these opens, the outdoor unit won’t run, yet the indoor blower can continue because its circuit is separate and the cooling call may still be active. This pattern exactly matches the scenario described: outdoor components shut off while the indoor blower stays on. A thermostat defect would more likely prevent a cooling call from being made, which could stop the blower as well, so it doesn’t pinpoint the outdoor shutdown. A faulty blower motor would stop the indoor air flow. A blocked condenser fan would cause performance issues or noise but doesn’t specifically explain why the protective switches would be open and stop the outdoor unit while the indoor blower remains energized.

When the indoor blower keeps running but the compressor and condenser fan are not, the outdoor unit is being kept from starting by safety/interlock devices rather than a simple thermostat or motor failure. The high‑pressure switch, low‑pressure switch, motor overloads, and the oil pressure switch are all designed to interrupt power to the compressor and the condenser fan if conditions are unsafe or abnormal. If any of these opens, the outdoor unit won’t run, yet the indoor blower can continue because its circuit is separate and the cooling call may still be active. This pattern exactly matches the scenario described: outdoor components shut off while the indoor blower stays on.

A thermostat defect would more likely prevent a cooling call from being made, which could stop the blower as well, so it doesn’t pinpoint the outdoor shutdown. A faulty blower motor would stop the indoor air flow. A blocked condenser fan would cause performance issues or noise but doesn’t specifically explain why the protective switches would be open and stop the outdoor unit while the indoor blower remains energized.