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93 MicroController Control System Troubleshooting
PROBLEM 38
Display = “Fc”, no lift truck operation.
POSSIBLE CAUSE
Direction contactor defect;
Drive motor defect;
Power connection defect;
Faulty of contactor coil wire;
Logic defect ;
Points
A) There is not good contact either on normally open of forward contactor or on normally closed of reverse contactor, due to
dust, dirt or any particles which prevent a valid contact. Clean contacts by means of compressed air ; if necessary remove dirt
applying a soft abrasive movement. It could be necessary changing both contactors.
B) There is not a good contact either on normally open of reverse contactor or on normally closed of forward contactor, due to
dust, dirt or any particles which prevent a valid contact. clean contacts by means of compressed air ; if necessary remove dirt
applying a soft abrasive movement. It could be necessary changing both contactors.
C) The most probably reason is that the normally closed contact of the braking contactor doesn't make a good contact towards
the battery negative for dust, dirt or because the contact doesn't lean completely for a mechanical defect of the contactor.
It may be due to 1 of follawing causes of motor connecting interruption :
1) brushes lift up from commutator
2) brushes cable burn up
3) Interruption either on motor winding or on motor itself cabling.
D) Forward contactor is supplied with a correct voltage but it doesn't close.
Possible causes:
1) contactor coil is interrupted, verify its resistance using an multimeter.
2) contact can't move due to mechanic block.
3) Nominal working coil voltage is greater than battery one.
CHECKS
Check conditions under which fault is detected.
Only at forward
running request
You see forward contator closing
for 0.3 sec then opening?
Yes No
Only at reverse
running request at both running
request
You see reverse contator closing
for 0.3 sec then opening?
Yes No
You see forward or reverse contator
closing for 0.3 sec then opening?
Yes No
See point D). See point G). See point E). See point H).
See point A). See point C). When requesting
forward running
you find any
voltage at a coil's
contact (or at
reverse contactor
coil’s contacts) for
0.3 sec?
Yes No
See point B). When requesting
forward running
you find any
voltage at coil
contactor for
0.3 sec?
Yes No
When requesting
reverse running
you find any
voltage at coil
contactor for
0.3 sec?
Yes No
See point F). See point I).