TM 5-3895-383-24
If the parking brake switch is moved to the OFF position and
the propel control lever is out of the NEUTRAL position, the
parking brake will remain engaged. When the propel control
lever is out of the neutral position, neutral start switch (4) is
open and relay "P9" (5) is de-energized. When relay "P9" (5)
is de-energized, current from fuse (3) goes through wire (12)
and relay "P7” (8). When the parking brake is ON, relay "P7"
(8) is energized in order to create a current path from wire (12)
to wire (13). Current flow through relay "P9" (5) and wires (12)
and (13) sustains relay "P7" (8) and relay "P6" (7) in an
energized state even if power to wire (14) is removed by
moving the parking brake switch to OFF. This keeps the
parking brake engaged and the propel pumps neutralized if the
parking brake switch is moved to the OFF position and the
propel control lever is out of the NEUTRAL position.
If the propel control lever is moved to the NEUTRAL position,
the neutral start switch closes and relay "P9" (5) is energized.
When relay "P9" (5) is energized, the current path to wire (12)
is disrupted. When no current is flowing through wire (12),
relay "P7" (8) and relay "P6" (7) will de-energize when the
parking brake switch (6) is moved to the OFF position. When
relay "P6” (7) de-energizes, interlock valves (9) and (10)
energize in order to release the parking brake. The propel
pumps are no longer prevented from upstroking when the
interlock valves are energized.
10-9
