TROUBLESHOOTING H-22
PC58UU-3
20-539
1
H-22 Machine cannot be steered sharply or steering force is insuf-
ficient
Cause Remedy
1
Does engine speed lower?
(Does engine speed lower
extremely only when machine
is steered during travel?)
NO
YES
Defective pump
servo
Repair or
replace
2
Is pressure at PP oil pressure
pickup port at top of control
valve equal to port pressure?
NO
YES
3
Does merging valve spool
move smoothly and is drilled
hole free of clogging?
NO
Defective operation
of merging valve
Repair or
replace
YES
Defective operation
of logic valve
Repair or
replace
4
Is drive pump pressure of
inside motor normal? (When
machine is steered along curve
about 5 m in radius on flat con-
crete, is inside pump pressure
below about 10 MPa {100 kg/
cm²})?
NO
YES
5
Is PPC pressure on the steered
side low?
NO
Defective PPC
Repair or
replace
YES
6
Does spool move smoothly?
NO
Defective operation
of spool
Repair or
replace
YES
Defective unload
valve
Repair or
replace
7
When check valve of main
relief circuit is replaced, is trou-
ble repaired?
NO
Defective counterbal-
ance valve of travel
motor or defective
swivel joint
Repair or
replace
YES
Defective check valve
of main relief circuit
Repair or
replace
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