JLG 120HX Service Manual - Manual (Page 106)

SECTION 3 - TROUBLESHOOTING
3-20 – JLG Lift – 3120819
Abrupt start-up of any functions: both directions.
Card “Low” potentiometer setting too high. Adjust “Low” potentiometer to “Just Start” func-
tion.
“High” and “Low” pots set too close together. Adjust per JLG Publication 3120351.
Slow function speed/engine lugs down at full throttle position.
Card “High” potentiometer set too low. Adjust “High” potentiometer until function speed
does not lug down.
Speed not proportional.
“High” and “Low” pots not adjusted properly. Adjust pots to factory specifications or refer to
JLG Publication 3120351 for proper adjustment.
Cylinder drifts or drive motor slowly rotates when controller is returned to neutral. (high null bias)
Controller failed, resulting in a command at neu-
tral position. Adjust or replace microswitch.
Microswitch remained open in controller. Replace microswitch.
Ramp too high in controller. Set ramp as needed.
Brakes not applying in swing or drive. Check brakes. Repair or replace as necessary.
Table 3-6.Electrical System - Troubleshooting
TROUBLE PROBABLE CAUSE REMEDY