JLG 1850SJ Service And Maintenance Manual page 385

Control operates pump in one direction only
No pump function
Erratic pump function
Erratic or no machine function
Item
Input to pump control
Pump control neutral
Item
Oil level in reservoir
Heat exchanger
Charge pressure
Charge pump inlet vacuum
System relief pressure settings
System pressure
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SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
Table 5-34. Electrical troubleshooting
Item
Control coil failure.
No power to controller.
Electrical connection to pump is bad.
External controller malfunction or
hydraulic system problem.
Table 5-35. Neutral difficult or impossible to find
Description
Input to control module is operating
improperly.
Neutral set improperly.
Table 5-36. System operating hot
Description
Insufficient hydraulic fluid will not meet cooling
demands of system.
Heat exchanger not sufficiently cooling the system.
Low charge pressure will overwork system.
High inlet vacuum will overwork system. A dirty fil-
ter will increase the inlet vacuum. Inadequate line
size will restrict flow.
If the system relief valves are worn, contaminated, or
valve settings are too low, the relief valves will be
overworked.
Frequent or long term operation over system relief
setting will create heat in system.
Description
Measure resistance at coil pins. Resistance
should be 14.2W (24V) or 3.66W (12V) at 20° C
[70° F]. Replace coil.
Restore power to controller.
Disconnect connection, check wires, recon-
nect wires.
Verify external controller problem using spare
controller. Replace controller. Check hydraulic
system fluid level/pressures/filters/etc. Fix
hydraulic system problems.
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.
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.
Fill reservoir to proper level.
Check air flow and input air temperature for heat
exchanger. Clean, repair or replace heat exchanger.
Measure charge pressure. Inspect and adjust or
replace charge relief valve. Inspect charge pump.
Repair or replace charge pump.
Check charge inlet vacuum. If high, inspect inlet filter
and replace as necessary. Check for adequate line
size, length or other restrictions.
Verify settings of high pressure relief valves and
replace valves as necessary.
Measure system pressure. If pressure is too high,
reduce loads.
Action
Action
Action
5-133