A heavy-duty hydraulic excavator's A/C system cycles rapidly (compressor clutch engages and disengages every 5-10 seconds) shortly after startup. Both high and low-side pressures are unusually low (e.g., low-side 100 kPa, high-side 500 kPa). What is the most probable cause of this symptom?

Question: A heavy-duty hydraulic excavator's A/C system cycles rapidly (compressor clutch engages and disengages every 5-10 seconds) shortly after startup. Both high and low-side pressures are unusually low (e.g., low-side 100 kPa, high-side 500 kPa). What is the most probable cause of this symptom?

Answer options: ✅ Insufficient refrigerant charge.

• A faulty expansion valve stuck in the open position.
• A restricted condenser airflow due to debris.
• An overcharged refrigerant system.

Correct answer: Insufficient refrigerant charge.

Explanation: Rapid cycling of the compressor, accompanied by abnormally low high and low-side pressures, is a classic indication of an insufficient refrigerant charge. The low-pressure switch opens due to lack of refrigerant, cutting power to the clutch, and then closes as pressure equalizes, repeating the cycle.