TM 5-5420-234-14&P
5-2. DIRECT SUPPORT TROUBLESHOOTING (continued).
3.
MAIN FRAME DOES NOT UNLOAD (continued).
COUNTERBALANCE VALVE TEST
WARNING
The main frame cylinders may be under
hydraulic pressure. Steps 1 through 3
must be performed to relieve hydraulic
pressure before removing counterbalance
valves from main frame manifold. Fail-
ure to comply with this warning may
result in damage to equipment and injury
to personnel.
NOTE
Hook arm and main frame must be in the
stowed position.
(1)
Turn engine switch to ON and light control
MAIN FRAME
PORT VB
switch to STOP LIGHT position.
MANIFOLD
(2)
Turn LHS MODE SELECT switch to AUTO
position.
(3)
Turn off engine and light control switches
after a minimum of three minutes.
NOTE
Oil will drip from main frame manifold when
counterbalance valve is removed.
(4)
Remove counterbalance valve from right
main frame manifold port VA.
(5) Remove counterbalance valve from right
main frame manifold port VB and install in
PORT VA
port VA.
(6) Install remaining counterbalance valve in
COUNTERBALANCE
right main frame manifold port VB.
VALVE
(7) Start engine and engage the PTO.
(8) Turn the light control switch to the STOP
LIGHT position. Place LHS MODE SELECT
switch in the HOOK ARM ONLY (manual
mode) position.
(9) Attempt to unload the main frame using the
remote control or cab controls. Note the
operation of the main frame.
(10) Shut off engine and turn light control switch
to OFF position.
(11) If the main frame now unloads properly, the
counterbalance valve installed in the right
manifold port VB is faulty. If the main frame
still does not unload, the counterbalance
valve in the left manifold port VA is faulty.
5-21
