JLG M450 ANSI Service Manual - Manual (Page 223)

SECTION 7 - BASIC TROUBLESHOOTING, ELECTRICAL INFORMATION, & SCHEMATICS
3121127 – JLG Lift – 7-9
.
Table 7-3. Turntable Assembly - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY
CONTROL VALVE.
Valve Spool Sticking.
Dirt in oil causing excessive temperature built-
up. Change oil using recommended viscosity and
flush system.
Incorrect valve mounting causing warping of the
unit. Loosen valve and check mounting.Repair as
necessary.
Valve spool scored. Remove valve and repair or replace as neces-
sary.
Return spring weak or broken. Remove valve and repair or replace as neces-
sary.
Relief valve malfunctioning causing excessive
pressure within valve. Check pressure delivery to and from valve and
repair or replace as necessary.
Valve leaking.
Dirt or other foreign material under seal. Remove and replace valve as necessary.
Valve spool scored. Repair or replace valve.
Excessive back pressure caused by restricted
return line to reservoir. Remove line and clear obstruction or replace line
as necessary.
Damaged valve seals. Repair or replace valve as necessary.