23
SC900 Troubleshooting
Problem
Possible Cause
Fix
Unit will not turn on.
No power.
1. Test 3 phase power.
2. Contact a TWE Rep.
Fan does not run.
Fan failure
1. Check fan for any obstructions.
2. 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. Remove the top cover and the cover of the black box
inside the machine. Locate Touch/Trigger Control Board
#16002. Check and note the operation of the 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 1.5 amp fuse next to breakers.
3. Check hand tool coil resistance (12 ‐ 40 ohms).
4. Remove side panel without louvers to examine lights on
the left circuit board. Report your findings to a TWE Rep
for troubleshooting assistance.
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.
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. Check and
note the operation of the driver LED’s and report the
status.
