What could indicate that there is an obstruction to airflow in an A/C system?

Excessive high-side pressure in an A/C system is a strong indicator of an obstruction to airflow. When there is an obstruction in the system, it can restrict the flow of refrigerant, causing a build-up of pressure on the high side. This occurs because the compressor continues to compress the refrigerant, but the obstructed flow prevents it from moving efficiently through the system, leading to elevated pressure readings.

High-side pressure typically reflects the refrigerant's temperature and the system's capacity to dissipate heat. An obstruction means that the heat transfer process is disrupted, which can result in the compressor working harder than normal to maintain the system's operation. In such a scenario, the pressure on the high side may rise significantly, indicating that something is impeding the normal flow of refrigerant through components such as the evaporator or condenser.

In contrast, high low-side pressure would suggest different problems, such as an overcharged system or issues with the expansion device, rather than specifically indicating an airflow obstruction. Insufficient coolant levels and a compressor not running could lead to other issues within the system but would not necessarily point to an airflow obstruction directly.