If the low-pressure gauge of a vapor-cycle cooling system stays in a vacuum after evacuation, what is the likely issue?

When the low-pressure gauge of a vapor-cycle cooling system remains in a vacuum after evacuation, it typically indicates a blockage in the system. In a functional cooling system, the low-pressure side should indicate a certain pressure corresponding to the presence of refrigerant. If the gauge is reading in a vacuum, this suggests that the refrigerant is not circulating properly, most likely due to an obstruction.

Blockages can occur in various components, such as the expansion valve, evaporator, or any line that restricts the flow of refrigerant. This obstruction prevents the normal operation of the system, causing a vacuum condition that the gauge reflects. Therefore, the vacuum reading serves as a clear indicator that there is a system failure, and further investigation into potential blockages is warranted.