JLG 1850SJ, Service And Maintenance Manual, Page: 385 / 712

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
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Table 5-34. Electrical troubleshooting
Item Description Action
Control operates pump in one direction only Control coil failure. Measure resistance at coil pins. Resistance
should be 14.2W (24V) or 3.66W (12V) at 20° C
[70° F]. Replace coil.
No pump function No power to controller. Restore power to controller.
Erratic pump function Electrical connection to pump is bad. Disconnect connection, check wires, recon-
nect wires.
Erratic or no machine function External controller malfunction or
hydraulic system problem. Verify external controller problem using spare
controller. Replace controller. Check hydraulic
system fluid level/pressures/filters/etc. Fix
hydraulic system problems.
Table 5-35. Neutral difficult or impossible to find
Item Description Action
Input to pump control Input to control module is operating
improperly. Disconnect input and check to see if pump comes back to neu-
tral. If Yes, input fault, replace/repair external controller. If No,
go to next step.
Pump control neutral Neutral set improperly. Shunt servo gauge ports M4 and M5 together with external
hose and see if pump comes back to neutral. If Yes: control neu-
tral improperly set. If no: balance swashplate (see Mechanical
neutral adjustment). If you still cannot set neutral, replace con-
trol.
Table 5-36. System operating hot
Item Description Action
Oil level in reservoir Insufficient hydraulic fluid will not meet cooling
demands of system. Fill reservoir to proper level.
Heat exchanger Heat exchanger not sufficiently cooling the system. Check air flow and input air temperature for heat
exchanger. Clean, repair or replace heat exchanger.
Charge pressure Low charge pressure will overwork system. Measure charge pressure. Inspect and adjust or
replace charge relief valve. Inspect charge pump.
Repair or replace charge pump.
Charge pump inlet vacuum High inlet vacuum will overwork system. A dirty fil-
ter will increase the inlet vacuum. Inadequate line
size will restrict flow. Check charge inlet vacuum. If high, inspect inlet filter
and replace as necessary. Check for adequate line
size, length or other restrictions.
System relief pressure settings If the system relief valves are worn, contaminated, or
valve settings are too low, the relief valves will be
overworked. Verify settings of high pressure relief valves and
replace valves as necessary.
System pressure Frequent or long term operation over system relief
setting will create heat in system. Measure system pressure. If pressure is too high,
reduce loads.