🔍 Key Concepts

• Refrigerant sight glass purpose – what does seeing clear liquid vs. bubbles usually tell you about system condition? • Refrigerant charge level – how does low refrigerant affect what you see in the liquid line? • Normal vs. abnormal conditions that could cause bubbles besides charge, such as excessive pressure drop or component malfunction.

💭 Think About

• Ask yourself: In a properly charged, normally operating system, what should the liquid line sight glass look like? • Which of these options would most directly cause vapor to appear in a line that is supposed to be carrying subcooled liquid? • Consider which options describe a condition (charge level) versus a specific component problem, and which would most consistently show up as continuous bubbles in the sight glass.

✅ Before You Answer

• Verify how a properly charged liquid line appears in the sight glass under normal load: clear or bubbly? • Check your understanding of insufficient refrigerant: does it tend to introduce vapor into the liquid line and sight glass? • Consider whether a faulty expansion valve or solenoid valve stuck open would necessarily and directly create bubbles in the liquid line sight glass, or if their effects are seen elsewhere.