What procedure should you perform if an SB-230 has high suction pressure during cooling?

When diagnosing high suction pressure in a Thermo King SB-230 during cooling, performing a low side pumpdown is the appropriate procedure. This method involves removing excessive refrigerant from the low side of the system, which can help to identify underlying issues causing the elevated pressure reading.

In a cooling cycle, high suction pressure could indicate that the system is overcharged or that there are restrictions or blockages in the low side of the refrigeration cycle. By conducting a low side pumpdown, the technician can reduce the pressure safely and assess the effects on system performance. This step allows for observation of whether the suction pressure stabilizes at a normal operating level, which can help in diagnosing problems related to refrigerant charge or system restrictions.

The other options, such as a compressor capacity test or combined heat test, serve different diagnostic purposes and may not specifically address the immediate problem of high suction pressure during cooling. The compressor pumpdown could be considered in some scenarios, but it typically pertains more broadly to system diagnostics rather than specifically targeting high suction pressure situations in cooling mode.