Priority switch valve (N185)
The priority shift valve connects the brake and clutch vacuum circuits.
When the engine is running, providing the brake servo is sufficient, the valve opens and the two vacuum circuits are shared, the electric pump is no longer required as the engine-driven vacuum pump exhaustes (provides vacuum to) both circuits. If the clutch circuit pressure drops below 0.5bar, the electric vacuum switches on, and the priority switching valve is CLOSED, thus, the electric vacuum pump provides vacuum to the clutch circuit only. If the brake circuit vacuum drops below 0.7bar whilst the engine is off in ecomatic operation, the engine is restarted immediately and the priority shift valve is closed.
When the engine is off (both by ignition and in coasting mode), the valve closes and the circuits are not connected.
Part number: 1H0 906 283 B