Actuator (Normal Position)

The solenoid valve spring holds solenoid valve against atmospheric air port and prevents air from entering vacuum chamber. Front side of diaphragm draws vacuum, and vacuum goes past solenoid valve to rear side of diaphragm. The spring holds diaphragm rearward. Rear brakes are connected through actuator hydraulic brake chamber, and function normally when actuator is in normal position (with port check valve held open by actuator piston rod). See illustration.