Why do the compressor and evaporator fan not run during defrost?

The compressor and evaporator fan do not run during defrost because the system should not be producing a cooling effect at that time. During the defrost cycle, the primary purpose is to remove accumulated ice from the evaporator coil, which occurs typically in refrigeration systems operating in cold conditions. If the compressor and evaporator fan were to continue operating, it would counteract the defrosting process by further cooling the coil, causing more icing rather than removing it.

The defrost cycle involves redirecting heat towards the evaporator coil to melt the ice build-up, and this heat is often provided by the compressor running in reverse or by auxiliary heaters. Thus, stopping the compressor and the evaporator fan during defrost ensures that the system focuses on raising the temperature of the coil to eliminate the ice effectively and restore proper functionality once the defrost is complete.