When first inspecting a hermetic system known to be leaking, you should look for which item?

• A. Hissing sounds at joints
• B. Frost around connections
• C. Traces of oil
• D. Discoloration of exterior casing

Answer: (C)

In a hermetic system, the lubrication oil travels with the refrigerant. When a leak occurs, the escaping refrigerant pulls some of that oil with it to the leak site, leaving visible oil traces around fittings or joints. This makes oil traces a direct and reliable clue to a leak, more dependable than frost, sounds, or surface discoloration, which can occur for other reasons or under varying conditions. Frost around connections can happen if the leak is cold enough and moisture is present, but it isn’t consistently present in every leak and depends on environmental factors. Hissing sounds may indicate a leak but aren’t always audible, and exterior discoloration can be unrelated to a leak. So, traces of oil are the most practical sign to look for when inspecting a hermetic system known to be leaking.