During compressor diagnosis on a rock drill, the clutch engages but the high-side pressure remains low (e.g., 400 kPa) and the low-side pressure unexpectedly rises (e.g., 500 kPa). The system has a full charge of R-134a. What is the most likely internal compressor fault?

Question: During compressor diagnosis on a rock drill, the clutch engages but the high-side pressure remains low (e.g., 400 kPa) and the low-side pressure unexpectedly rises (e.g., 500 kPa). The system has a full charge of R-134a. What is the most likely internal compressor fault?

Answer options: ✅ Internal compressor valves are stuck open or damaged.

• The compressor shaft has seized internally.
• The compressor clutch coil is shorted.
• The compressor's piston rings are worn out.

Correct answer: Internal compressor valves are stuck open or damaged.

Explanation: If the clutch is engaged but the compressor fails to build high-side pressure while the low-side pressure rises significantly, it indicates that the compressor is not effectively pumping refrigerant. This is characteristic of internal damage such as stuck-open or damaged reed valves that prevent proper compression and flow within the compressor. Worn piston rings also contribute but valve failure is more direct cause.