23
SC2402
Troubleshooting
Problem
Possible
Cause
Fix
Unit
will
not
turn
on.
No
power.
1.
Test
3
phase
power
to
control
contactor.
2.
Check
taps
(if
applicable)
on
main
transformer.
3.
Check
voltage
selection
plug
near
control
transformer.
4.
Check
fuse
located
on
control
transformer.
5.
Look
for
power
available
LED
on
control
transformer.
6.
Make
these
checks
before
contacting
a
TWE
Rep.
Fan
does
not
run
when
unit
is
turned
on.
This
is
normal.
The
fan
will
cycle
on
when
the
main
bridge
has
reached
nominal
operating
temperature.
Ambient
temperature
of
the
weld
site
should
also
be
taken
in
consideration.
Fan
runs
continuously
(does
not
cycle
on/off)
Thermostat
circuit
A
fault
in
the
thermostatic
circuit
will
cause
the
fan
to
run
continuously.
Call
your
TWE
Rep
for
repairs.
Unit
turns
on,
coil
boot
test
is
good,
no
trigger
from
weld
gun.
Bad
connection
or
faulty
equipment.
1.
Test
control
cable
by
plugging
weld
tool
directly
into
unit
(4
conductor
straight
through
wiring).
2.
Check
gun
trigger
resistance
(<100
ohms
when
closed).
3.
Check
to
see
if
trigger
LED
on
control
panel
responds.
4.
Check
to
see
if
weld
tool
is
wired
according
to
one
of
the
three
diagrams
in
Chart
A
(see
page
25).
5.
Locate
Touch/Trigger
Control
Board
#16002
(Chart
B).
Check
and
note
the
operation
of
the
driver
LED’s
and
report
the
status.
Unit
turns
on,
no
coil
test,
no
lift
from
gun
coil,
trigger
is
good.
Bad
connection
or
faulty
equipment.
1.
Test
control
cable
by
plugging
weld
tool
directly
into
unit
(4
conductor
straight
through
wiring).
2.
Check
10
amp
fuse
on
control
board
box
next
to
break
‐
ers.
3.
Check
hand
tool
coil
resistance
(12
‐
40
ohms).
4.
Locate
Touch/Trigger
Control
Board
#16001
(Chart
B).
Check
and
note
the
operation
of
the
driver
LED’s
and
report
the
status.
Gun
lifts,
no
weld
arc
drawn.
Bad
connection
or
faulty
equipment.
1.
Check
connections
for
ground
and
weld
tool
leads.
2.
Check
if
contact
LED
on
control
panel
lights
when
stud
is
touched
to
work
surface
(closing
circuit).
3.
Check
the
two
circuit
breakers
on
the
control
board
box.
4.
Check
to
see
if
you
have
the
sustaining
arc
(a
small
blue
arc
for
the
duration
of
the
weld
time).
5.
Check
to
see
if
the
stud
sparks
at
the
end
of
the
weld
cycle
(hot
plunge).
6.
Locate
Touch/Trigger
Control
Board
#16001
(Chart
B).
Check
and
note
the
operation
of
the
driver
LED’s
and
report
the
status.
