Technician A says pinhole leaks in the evaporator may be caused by acid formed when water and refrigerant are mixed. Technician B says leaks are most often found at hose connections and at the various fittings and joints in the system. Who is correct?

Pinhole leaks in the evaporator can indeed be attributed to various factors, including the presence of acid that forms when water mixes with refrigerant. The combination of moisture and refrigerant can lead to corrosion, which is a key cause of these small leaks. This chemical reaction diminishes the integrity of the metal over time, ultimately resulting in pinhole leaks. Therefore, Technician A's statement accurately describes one potential cause of pinhole leaks.

Additionally, leaks are frequently found at hose connections and various fittings and joints in the system. These areas are under considerable stress due to movement, temperature changes, and pressure variations. Over time, these factors can cause wear and tear, leading to leaks. Technician B's observation aligns with common experience in HVAC maintenance practices, where these points are monitored for potential errors.

Since both technicians make valid points regarding the sources of leaks in evaporators, both statements are correct, which justifies the selection of the option stating that both A and B are correct. This understanding helps in diagnosing and addressing leaks effectively in air conditioning and heating systems, promoting better maintenance practices.