OEM replacement switch assembly for the SHURflo® PowerTwin 12-volt diaphragm pump (model 4111-035). The pressure switch monitors system pressure and automatically cycles the pump on and off on demand. A faulty switch causes symptoms like the pump running continuously, failing to shut off at pressure, or not turning on when flow is needed. Replacing the switch assembly restores full automatic demand operation. Fits PowerTwin models only — not compatible with standard 2088 Series pumps.