JLG 460SJ ANSI Service Manual - Manual (Page 144)

SECTION 3 - CHASSIS & TURNTABLE
3-90 – JLG Lift – 3120788
3.23 TROUBLESHOOTING OF THE SKY
WELDER
Low Sky Welder Speed
If the welder/generator is running below 3600 RPM, the
welder or generator can not function properly. Low speed
is caused by only three factors.
1. Low hydraulic flow.
2. Mis-adjusted flow regulator.
3. Worn hydraulic motor.
Carefully loosen the lock nut on the adjustment screw and
on top of the flow regulator located on the ed of the
hydraulic motor. While monitoring the speed slowly turn
the adjustment screw with an allen key counterclockwise
to increase speed. If you do not see an increase by turn-
ing the screw a quarter to a half a turn, return the screw to
the original position and lock the lockout. This was an
indication that the flow coming to the regulator is too low.
Your problem could be engine speed or a worn hydraulic
pump. If the welder speed increases turn the adjustment
screw so the welder rotates at 3700 RPM no load, lock
adjustment nut.
Low Welding Amps
Low welding amps can be caused by three components.
Excitation Bridge located on the bottom right hand corner
- defective. The second component that could cause this
is an open fine control. Resistance should be 6 ohms. A
thermal trip i the windings. Disconnect the two AC wires
off the bottom right hand Excitation Bridge (white &
orange) and take a resistance reading. With the seven-
step selector switch inn the lowest position and range
switch in the highest position you should get about 2
ohms. Move the seven-step switch while observing the
ohmmeter all the way to its highest position. The resis-
tance should increase slightly with every step. You should
end up with about 3 ohms. If you do not start off with 2
ohms and the circuit shows open move your ohmmeter
lead over 1 lead to the center terminal on the range
switch, the other ohm meter lead onto the terminal RL1 on
the seven position switch.If you have a reading, there
about 2 ohms the transformer is ok.To test for the terminal
trip in a winding take a reading between the center post of
the range switch and the white wire you removed from the
Excitation Bridge. You should get 0 ohms. Any other read-
ings on the trip is defective. To check the fine control put
one ohmmeter lead on the seven-step switch terminal
RL1, the other lead on he orange wire you removed from
the Excitation Bridge. You should be able by moving the
fine control up and down adjust the ohmmeter reading
between 0 and 6 ohms. To check the Excitation Bridge,
remove all wires from it and measure forward and back-
ward going around clockwise. In any position and in any
combination between terminals you should get a high and
low reading. If any one of the readings come out the
same, the bridge is defective.
No Output on Weld Receptacles or AC
Receptacles
This problem can be caused by many different factors. At
rare occasions a welder/generator could lose it’s residual
magnetism, which will cause the welder to be completely
dead. To re-energize the magnetism remove the recepta-
cle panel. Locate the two excitator bridges on the bottom
left and bottom right, pull off the red and black wire com-
ing from the brushes on the left bridge and the red wire
jumped over to the right bottom bridge. With an ohm
meter check resistance between red and black wire which
will check the resistance off the rotor, this should be about
22 ohms, try to rotate the rotor while you take the reading
to be sure the brushes are receded, if the reading is inter-
mitted check the resistance at the right on the slip rings. If
necessary, remove the brush holder (see brush holder
replacement). Apply 12 volts to the terminals on the red
and black wire coming from the brush holder. Apply 12
volts for about 15 seconds. Re-install wires, re-install
receptacle panel and start welding.
No Ac Output but Weld Output
If the welder section functions properly but you have no
AC output remove the receptacle panel and make sure
the white four terminal plugs are plugged solid. If they are
connected all the way, disconnect and take resistance
reading as follows.
a. Blue to Brown (1.2 ohms)
b. Black to White (1.2 ohms)
If either one of these two readings is open the AC wind-
ings are defective. If they both check out ok, check the
receptacle and the wires going to the receptacle. To be
certain that it is in the receptacle panel wiring, very care-
fully start up the welder and check for 120 volts AC
between Blue and Brown and again 120 volts AC between
Black and White. If you have 120 volts AC pressing at
those two readings, you must have a defective receptacle
or receptacle wiring.