Which of the following is a sign of a refrigerant leak?

A refrigerant leak is indicated by bubbling in soapy water because the soap creates a barrier that captures gas escaping from any joint or leak point in the system. When refrigerant leaks from the system, it interacts with the soap solution, forming bubbles at the point of escape. This method is commonly used in the field to visually detect leaks in refrigeration systems.

Consistent pressure readings suggest that the system is operating normally, which would not point to a leak. Cool air from the vents indicates that the refrigerant is circulating and performing its job of cooling the air, which is also a sign of proper function, not a leak. Normal operation of the compressor means it is effectively compressing and circulating the refrigerant without issues, again suggesting no leakage is occurring. Thus, bubbling in soapy water stands out as the definitive sign of a refrigerant leak.