TM 9-3431-254-14&P
CONTROL BOX MALFUNCTION TROUBLESHOOT.
DC between the coil and ground for a minimum of 10
ING lNSTRUCTIONS
seconds after the engine starts. If not, the control box
The control box used on the GCC-300-W is composed of
timer board is probably malfuctioning. If there is 12
several printed circuit boards. However, troubleshooting
volts DC at this point, check the engine oil pressure
is no more difficult than troubleshooting conventional
and low oil pressure switch for proper operation.
control circuits. Do not overlook the obvious. As in the
case of all electrical equipment loose connections are
3. CONTACTOR WILL NOT CLOSE
the primary cause of malfunction, both internal and
external to the welding machine. In general, the things
a. Using a VOM, measure the voltage between the
to look for are: bad grounding connections, worn con-
contactor coil and ground. This value should be 115
volts DC If you have no voltage, but have 115 volts
tact tubes (tips), dirty cable liners, shorted control
cables, wrong control settings, blown fuses, worn con-
AC at the receptacles, the contactor control board is
probably faulty. Replace the control box assembly.
tactors, and misconnection from wire feeding equipment.
The only equipment needed to property detect problems
b. If there is 115 volts DC between the contactor
in this control box is a simple volt-ohm meter. If the
coil and ground, the contactor coil is probably faulty.
control box is suspected of being the cause of a prob-
Replace contactor.
lem, first check the fuse on the top of the control box,
If it is blown replace with a 10 ampere fuse.
4. NO AC VOLTAGE
a. Check fuse in field flashing circuit on control
1. ENGINE WON'T START
panel. If fuse is blown, replace with 4 ampere fuse.
& Check to see if the relay on top of the control box
b. Measure voltage between exciter positive slip ring
is closing. If not check with volt-ohm meter (VOM) to
and ground while starting. It should be 12 volts DC; if
make sure that 12 volts DC power is present on pin
not, the voltage regulator board is probably faulty. Re-
10 (yellow-wire), with the ignition switch in the RUN
place the control box assembly.
position, and in the START position. Also check pin
12 (brown wire) for 12 volts DC with the ignition
c. If there is 12 volts DC between the slip ring and
switch in the START position. If these tests show 12
ground. the exciter is not building up, and there is
volts DC at these points, the malfunction is probably
probably nothing wrong with the control box. See Loss
in the control box, which should be exchanged. No
of Magnetism.
attempt should be made to repair the box.
5. HIGH AC VOLTAGE
2. ENGINE STARTS BUT WILL NOT CONTINUE
TO RUN
a. Adjust the voltage regulator by removing the con-
trol box cover and adjusting' the potentiometer in the
a. Using a VOM, check for 12 volts DC current
upper right-hand and corner of the control box. If this does
between the positive terminal on the ignition coil, and
not bring the AC voltage down, the voltage regulator is
ground during starting, and after the ignition switch is
probably faulty, and the control box assembly should
released to the RUN position. There should be 12 volts
be replaced.
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