Page 40
Systems Descriptions
M268 Hydraulic Pump: Fixed displacement external
gear type hydraulic pump with 12 VDC electric motor
and 76 cubic inch fluid reservoir. The pressure relief
valve is factory set at 2100 psi. The Braun Pump
Code for front or rear mounted 12 volt M268 pumps
is 30. Note: 24 Volt pumps are available for special
applications and have a Braun Pump Code of 31.
Pump Modules: Pump modules are available as a
complete quick-service repair unit. See the Pump
Module sections for detailed breakdowns on pages
58 through 61.
Hydraulic Fluid: Use Dextron III automatic trans-
mission fluid. Make sure the platform is fully
lowered and roll stop is fully unfolded when
checking fluid level or adding fluid. Fill to within 1/2"
of the bottom of the 1-1/2" diameter fill tube (neck).
The maximum fluid level is designated on the pump
reservoir with decal 26735. DO NOT use a solid plug
or fill cap without a breather hole. Doing so will result
in pump and/or reservoir damage.
Contamination: Fluid should be changed if there is
visible contamination. Inspect the hydraulic system
(cylinder, hoses, fittings, seals, etc.) for leaks if fluid
level is low.
Cold Weather Applications: The oil can be thinned
with two (2) tablespoons of diesel fuel. The oil should
be changed when warm weather returns. Note: We
recommend SAE 10 W non-detergent oil mixed by
volume with no more than 30% #1 fuel oil or kero-
sene for full time cold weather applications.
Pump Mounted Electrical “Unfold” Solenoid/
Hydraulic Valve: When the platform is in the stowed
(fully-folded) position, pressing and holding the
UNFOLD switch circuit energizes this solenoid/valve
(the Bridging and Down Solenoid/Valves are ener-
gized also). When energized, it directs the flow of
hydraulic fluid to the internal manifold orifice (flow is
through internal manifold pressure compensator
during the de-energized status). The manifold orifice
meters a limited rate of hydraulic fluid flow from the
lift cylinders during the unfold cycle to reduce the rate
of the platform deployment.
When the platform unfolds fully (reaches floor level),
the Unfold/Down microswitch is deactivated (at rest).
Deactivating this microswitch interrupts the UNFOLD
(Out) switch circuit and redirects current to the DOWN
switch circuit to re-energize the Bridging and Down
solenoid/valves when the DOWN switch is pressed.
Troubleshooting: A problem with this solenoid/
valve can be electrical or hydraulic. Follow the
Quick-Check troubleshooting procedure detailed
the Solenoid/Hydraulic Valve section on page 35
when troubleshooting.
Pump Mounted Electrical “Bridging” Solenoid/
Hydraulic Valve: When the platform is in the
stowed (fully-folded) position, pressing the UNFOLD
switch energizes this solenoid/valve. When the
platform reaches floor level, the Bridging solenoid/
valve is de-energized by the Unfold/Down mi-
croswitch circuit. Releasing the UNFOLD switch
also de-energizes this solenoid/valve.
This solenoid/valve is also energized while the
DOWN switch is pressed (when the platform is fully
unfolded). It will remain energized until the DOWN
switch is released or the bridging microswitch is
deactivated. If the bridging microswitch is deacti-
vated, the bridging solenoid/valve is de-energized
which prevents fluid from flowing from the lifting
hydraulic cylinders to the reservoir and stops the
lowering of the platform (while allowing oil flow from
the roll stop cylinder - roll stop deploys).
Troubleshooting: A problem with this solenoid/
valve can be electrical or hydraulic. Follow the
Quick-Check troubleshooting procedure detailed
the Solenoid/Hydraulic Valve section on page 35
when troubleshooting.
Pump Mounted Electrical “Down” Solenoid/
Hydraulic Valve: The UNFOLD switch circuit
energizes this solenoid/valve which allows hydraulic
fluid to return from the cylinders to the reservoir at a
limited rate, thus allowing gravity to unfold the
platform. Fluid flows through the internal manifold
valve and orifice before reaching the Down valve.
The Unfold/Down microswitch is deactivated (at
rest) when the platform unfolds fully (reaches floor
level), which interrupts the UNFOLD switch circuit,
thereby de-energizing the solenoid/valves. Releas-
ing the UNFOLD switch de-energizes this valve
also. This stops and holds the platform at the
current position by stopping the flow of hydraulic
fluid from the cylinders to the reservoir.
When the platform unfolds fully to floor level and the
Unfold/Down microswitch is deactivated (at rest),
Hydraulics
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