Chapter 3 Crane Reference 27
Control Valve Troubleshooting Chart
Theory of Operation – The control valve for this crane family consists of an electro-hydraulic
proportional valve with integral bypass which feeds four series on/off solenoid valves. The
proportional valve controls function speed. The on/off solenoid valves control which functions are
operated and the direction of operation. The valve manifold also includes a relief valve to limit
system pressure, a winch brake vent solenoid to apply the brake of a planetary winch, and a
high speed lower solenoid valve for the lift circuit. The proportional valve and the on/off valves
incorporate manual overrides for troubleshooting and emergency operation. The swing valve
uses a counterbalance valve in each work port to block flow in neutral. The swing brake shuttle
valve is not used for this application.
FUNCTION / ISSUE ACTION
WINCH
Check operating pressure at valve inlet, Port G.
1. Check and/or adjust main relief valve, Valve G. (Pressure setting - 3000 psi
-0/+100 psi)
2. Check and/or adjust outrigger relief valve, if unit is equipped with outriggers.
(Pressure setting - 3500 psi)
3. Engage proportional valve (Valve A) manual override while operating
function. If winch operates,
a. Verify power to Valve A.
b. Check Valve A for contamination.
4. Engage winch on/off control valve (Valve B) manual override while
operating function. If winch operates,
a. Verify power to Valve B.
b. Check Valve B for contamination.
Winch will not operate in either
direction.
5. Check winch counterbalance valve and PO check valve for contamination.
1. Check items 1 through 5 for "Winch will not operate in either direction."
2. Disconnect brake line and cap both ends to winch brake vent solenoid valve
(Valve F). If winch begins to lower:
a. Verify power to Valve F.
Winch will not lower.
b. Check Valve F for contamination.
EXTEND
1. Check items 1 through 3 in "Winch will not operate in either direction."
2. Engage extend on/off control valve (Valve C) manual override while
operating function. If extend operates:
a. Verify power to Valve C.
Extend cylinder will not extend.
b. Check Valve C for contamination.
1. Check items 1 and 2 for "Extend cylinder will not extend." Extend cylinder will not retract.
2. Check extend counterbalance valve for contamination.
LOWER
1. Check items 1 through 3 for "Winch will not operate in either direction."
2. Engage lower on/off control valve (Valve D) manual override operating
function. If lower operates:
a. Verify power to Valve D.
Lower cylinder will not extend.
b. Check Valve D for contamination.
1. Check items 1 and 2 for "Lift cylinder will not extend." Lower cylinder will not retract.
2. Check lower counterbalance valve for contamination.
1. Verify power to high speed lower valve (Valve H). Premature kick out of overload
system during rapid lowering of
a heavy load.
2. Check high speed lower valve for contamination.
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