Which of the following is NOT a cause of high side pressure above specs in an A/C system?

A broken compressor reed valve does not contribute to high side pressure being above specifications in an A/C system because its failure would likely lead to reduced pressure or operation inefficiencies rather than increased pressure. The reed valve is essential for controlling the flow of refrigerant from the compressor into the condenser; if it is not functioning properly, it either fails to open or close correctly, resulting in a loss of refrigerant compression and a corresponding drop in pressure on the high side.

In contrast, options such as overcharging the refrigerant, having restricted airflow across the condenser, or a plugged expansion valve directly lead to increased high side pressures. An overcharge results in excess refrigerant entering the system, causing higher pressure. Restricted airflow across the condenser impedes heat removal, which can also elevate high side pressure. A plugged expansion valve prevents proper expansion of refrigerant, contributing to elevated pressure levels. These scenarios all directly influence the high side pressures within the system.