1.16 HYDRAULIC SYSTEM Continued.
Placing the control switches in the positions corresponding to the above modes opens solenoid valves SV2
and SV5 and closes solenoid valves SV7, SV9, and valve PD1 by applying +24 Vdc to the coils. All remaining
solenoids remain in their normal de-energized positions. The engine driven pump, through a combination of
gravity and suction, draws fluid from the hydraulic reservoir in the ECU and supplies pressure to the
hydraulic control manifold. Fluid flows through the vent (NBC) fan, M3. The fluid is returned to the
manifold where it is divided by flow control, FP3. Part of the fluid is supplied to the recirculation fan, M2,
and the balance is diverted around the motor in order to maintain proper speed control. With solenoid valve
SV5 open and solenoid valve SV7 closed, the fluid is blocked from returning to the reservoir. This forces the
fluid over the heating system relief valve, RD2. The hydraulic fluid pressure at this point is approximately
2,600 psi. As the fluid passes over the relief valve (from the high pressure side to the low pressure side) heat
is generated in the fluid. The hot fluid then flows through the heating coil, HX-1A, where air flowing across
the coils picks up heat from the hot hydraulic fluid to warm the interior of the CBPS. After the fluid passes
through the heating coil, HX-1A, it is routed to the oil cooler, HX-2, filter, F1, and reservoir.
Figure 1-17. Static Mode, Internal Power,