JLG 740AJ, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3121160 3-219
5. Oil carryover a. Oil level overfull
b. Plugged oil scavenge line
c. Discharge pressure too low
d. Defective coalescer
a. Drain to correct level
b. Remove and clean
c. Check minimum pressure valve
d. Replace
6. Compressor overheating a. Insufficient oil
b. Restricted cooling air flow
c. Fan not operating
d. Plugged oil filter
e. Cooler core plugged
f. Pressure set too high
g. Contaminated cooler core
h. Running too fast
i. Thermal Valve – element faulty
a. Check level and top up
b. Reposition machine
c. Check ground connection; Check fan switch; Check air
pressure switch; Check circuit breaker; Check for shorted
wires; Check fan motor
d. Replace
e. Clean
f. Readjust
g. Remove and clean
h. Check hydraulic flow & pressure
i. Replace
7. System retains pressure after shutdown a. Solenoid valve stuck
b. Leak back from airline
a. Should be no power to solenoid valve Valve stuck.
Replace Pressure switch faulty/replace
b. Check minimum pressure valve for leak
8. Compressor stalls a. Belts slipping
b. Insufficient hydraulic system pressure/flow. This can
occur if another hydraulically activated component is used
off same pump system. Activating the secondary compo-
nent may drop hydraulic supply system pressure/flow and
leave insufficient for compressor. NOTE - even a momentary
drop in supply hydraulic supply pressure/ flow may initiate
compressor blowdown to commence.
c. Pressure relief valve set too low
d. Leak in seals on pressure relief valve
e. Air pressure set too high for hydraulic system
f. Leak in solenoid valve cartridge (directional flow control
valve) on manifold
g. Check over-pressure or over-temperature
a. Readjust/tighten
b. Check setting on supply pressure system relief valve.
Check to ensure adequate pressure/ flow. Check if other sys-
tems activated off same supply.
c. Check & reset
d. Remove & check seals or fit new valve cartridge
e. Adjust pressure switch to reduce air pressure.
f. Remove & check seals or fit new valve cartridge.
Table 3-18. Air Compressor Troubleshooting
SYMPTOM PROBABLE CAUSE SOLUTION