JLG 18RS Service Manual - Manual (Page 122)

SECTION 5 - HYDRAULICS
5-32 – JLG Lift – 3121284
Troubleshooting
Table 5-1. Electrical Troubleshooting
Item Description Action
Control operates pump in one direction only. Control coil failure Measure resistance at coil pins. Resistance should be 14.20 Ω (24V) or 3.66 Ω
(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, reconnect wires.
Filter bypass indicator switch Filter switch may be bad. Check/replace filter switch. Add gauge to filter bypass port to verify proper fluid
flow and verify switch operation by measuring resistance. open resis-
tance=>510 Ω, closed resistance<=122 Ω
Table 5-2. System Operating Hot
Item Description Action
Oil level in reservoir. Insufficient hydraulic fluid does not meet cooling
demands of system. Fill reservoir to proper level.
Heat exchanger. Heat exchanger is 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 overworks 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 overworks system. A dirty filter
increases 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 get over-
worked. Verify settings of pressure limiters and high pressure relief valves and adjust or
replace as necessary.
System pressure. Frequent or long term operation over system relief set-
ting creates heat in system. Measure system pressure. If pressure is too high, reduce loads.