Which of the following does NOT contribute to lower than normal high-side pressure?

A missing air dam does not contribute to lower than normal high-side pressure because the high-side pressure in an air conditioning system is primarily influenced by the refrigerant flow and the operation of the compressor rather than the airflow from the condenser. The air dam's role is to optimize airflow across the condenser, improving its heat exchange efficiency, but its absence doesn't directly reduce high-side pressure levels.

In contrast, a low refrigerant charge diminishes the amount of refrigerant available for heat absorption and can lead to lower pressures overall as the system struggles to maintain performance. A worn compressor can result in lower pressures because it may not be able to effectively compress the refrigerant to the required pressure levels, leading to inadequate system performance. Similarly, a restricted orifice tube can cause an imbalance in the system's pressure, leading to lower high-side pressures as the flow of refrigerant is impeded. These factors directly affect the refrigerant cycle and pressure readings, unlike the airflow management that the air dam is responsible for.