After performing an A/C system evacuation with an approved vacuum pump, a technician isolates the system and observes that the vacuum pressure rises from -98 kPa (-28.9 inHg) to -70 kPa (-20.7 inHg) over a 15-minute period. What does this observation indicate?

Question: After performing an A/C system evacuation with an approved vacuum pump, a technician isolates the system and observes that the vacuum pressure rises from -98 kPa (-28.9 inHg) to -70 kPa (-20.7 inHg) over a 15-minute period. What does this observation indicate?

Answer options: ✅ There is a refrigerant leak in the system.

• Residual moisture is boiling off within the system.
• The vacuum pump is faulty and not achieving a deep enough vacuum.
• The manometer used for measurement needs recalibration.

Correct answer: There is a refrigerant leak in the system.

Explanation: A vacuum decay test, where the system is isolated after evacuation and monitored for pressure rise, is a critical step to identify leaks. If the vacuum pressure rises significantly and stabilizes above the desired deep vacuum level after isolation, it strongly indicates the presence of a leak allowing atmospheric pressure into the system.