THEORY OF OPERATION - CONTINUED
BRAKE AND HYDRAULIC FAN SYSTEM - CONTINUED
Operation at Brake Cut-In Pressure. When brake system pressure is below cut-in pressure, brake sys-
tem receives a higher priority than fan system. Priority valve is closed and pump flow to fan motor is
Operation with Fan Speed Solenoid De-Energized.
(a) Fan system has priority when brake system pressure is at cut-out pressure. Fan speed solenoid controls
pump load sensing pressure when brake system is fully charged. Fan speed solenoid is a proportional
solenoid. As current to fan speed solenoid increases, output pressure decreases. When fan speed sole-
noid is de-energized, output pressure to load sensing port is at maximum. Pump will be fully stroked
and send maximum flow to fan motor. Thus, fan motor is turning at maximum speed.