Automotive Service Excellence (ASE) Air Conditioner Certification 2025 – 400 Free Practice Questions to Pass the Exam

Observing oil streaks in the A/C sight glass typically indicates that the refrigerant charge is low. In air conditioning systems, oils are used to lubricate the compressor and other moving parts. When the refrigerant level is insufficient, it can cause the oil to migrate out of the compressor and into other parts of the system, including the sight glass.

In this scenario, the presence of oil in the sight glass suggests that the refrigerant is unable to adequately transport the oil throughout the system due to the low refrigerant level. Under normal operating conditions with an adequate refrigerant charge, the sight glass should be free of oil streaks, showing a clear view of the refrigerant instead. This helps ensure proper lubrication and functioning within the A/C system. Properly charged systems prevent oil from accumulating visibly in the sight glass, reinforcing the understanding that oil streaks are a sign of an issue, most notably low refrigerant.