Which of the following repairs would ALWAYS be considered "major" under EPA's regulations?

The reason that the replacement of an evaporator coil is classified as a "major" repair under the EPA's regulations is due to the significance of the component within the refrigeration cycle. The evaporator coil plays a crucial role in absorbing heat from the environment, thereby allowing the system to cool effectively. Repairing or replacing this component usually involves a substantial amount of work, including the potential need to reclaim refrigerant, pressure testing, and possibly retuning the system after installation.

In contrast, the other options typically involve less extensive work and do not impact the fundamental operation of the system to the same degree. For instance, replacing a filter drier or a switch generally requires less effort and does not involve significant alterations to the system's core functions. These components can often be accessed and replaced without extensive disassembly of the air conditioning system. As a result, they are not classified as major repairs under the EPA's regulations, which focus on repairs that have a more extensive impact on system integrity and performance. A purge unit also does not typically warrant the classification of major repairs due to the nature of its functionality and replacement process.