Which of the following is a common cause of compressor short cycling and how would you diagnose it?

• A. Dirty condenser only; diagnose by replacing condenser.
• B. Restricted airflow only; diagnose by cleaning ducts.
• C. Faulty thermostat, pressure switch trips, overheating, restricted airflow, incorrect refrigerant charge, or dirty condenser; diagnose by checking electrical controls, temperatures, pressures, and airflow along with charge.
• D. Color of refrigerant oil.

Answer: (C)

Short cycling happens when the compressor starts and stops rapidly because the system hits a protection limit or operates in an out-of-range condition. The best option recognizes that many different factors can trigger this behavior and provides a practical, thorough way to diagnose them. A faulty thermostat or pressure switch can prematurely end cycles, overheating can trip protection, restricted airflow and improper refrigerant charge can push pressures and temperatures beyond normal, and a dirty condenser can raise head pressure. All of these end up causing the control to shut the compressor off sooner than it should or to restart soon after, creating short cycles. Diagnosing correctly means checking the electrical controls (thermostat, pressure switches, relays, and overloads), measuring temperatures (especially suction and evaporator temperatures) and pressures (suction and discharge pressures), assessing airflow (condenser and evaporator), and verifying the refrigerant charge. If any of these areas are out of spec, address it—correct thermostat or switch operation, fix leaks or adjust charge, improve airflow, clean or service the condenser, and ensure electrical wiring and protections are functioning properly. The color of refrigerant oil is not a diagnostic factor for this symptom.