Troubleshooting - Lincoln Electric SHIELD-ARC 400AS-50 Operating Manual

12V Starter - Read in conjunction with Wiring Diagram AM3062-E1, in this Manual. See page 18
TROUBLE
Machine fails to start
Machine starts, but has
the following faults:
Voltage at AC outlet,
but no voltage or
reduced voltage at
welder output studs.
There is no output from
either the AC outlet
or the welder output
studs
Machine has low
welding output or
fails to hold
welding current
constant.
Page 10

TROUBLESHOOTING

Numbers in brackets key in to items on diagram.
CAUSE
Check for:
Flat battery and/or faulty terminal connections.
Key switch (4) faulty connection and/or loose wires.
Starter motor faulty (21).
Check DC voltage across bridge rectifier (8). If there is
no voltage or half voltage, bridge rectifier may have
open circuit in one or two diodes only.
If the above is ok. then check:
Rheostat (9) for open circuit.
Shunt coil (9A) for open circuit.
Bad connections.
Check fuse F4. If F4 is blown also check
bridge rectifier (8).
If the above are ok., then check flashing circuit for
faults.
Check there is battery voltage across rotor brushes
(12A) with key switch (4) turned midway between Run
and Start position. If not, check for:
Flashing diode (10) open circuit.
Blocking diode (11) open circuit.
Key Switch (4) faulty.
Poor connections.
If the above are ok., then check for:
Bridge rectifier (8) open or short circuit.
Rotor (12) open or short circuit.
(Rotor resistance approx. 11 ohm.)
Capacitors (13) faulty.
Stator field windings (17) open or short circuit.
Alternator brushes (12A) sticking or excessively worn.
Dirty slip rings (12A).
Poor connections.
Rectifier bridge (8) may be open circuited on one or
two diodes only.
Main brushes excessively worn (7).
Faulty capacitors (13).
Rotor (12) or brushes (12A) may have a ground.
Electrode lead or work lead connections may be poor
Brush springs may be broken (7).
Main brushholder rocker (7) moved position.
Commutator may be dirty (7A).
2 segments on commutator burnt (7A) (open in that coil).
Shield-Arc 400AS-50
WHAT TO DO
Charge battery and/or clean terminals
Repair or replace
Repair or replace
Replace
Replace
Repair or replace
Repair
Replace
Replace
Replace
Replace
Repair
Replace
Repair or replace
Replace
Repair or replace
Free or replace
Clean
Repair
Replace bridge
Replace brushes
Replace capacitors
Locate and remove ground
Tighten all connections
Replace brush springs
Realign drilled marker points
Refer maintenance section page 6
Repair or replace
IMA 554C