Taylor-Dunn R 380-36, Operator'S And Service Manual

Page: 155 / 260

Sevcon Troubleshooting
Page 15
Electrical Troubleshooting
Test 8. ANTI-ROLLOFF FAULT
The Sevcon Controller is equipped with a feature called Anti-Rolloff. Anti-Rolloff will
automatically slow the vehicle if it starts to roll. Anti-Rolloff is active when the key switch has
been left in the “ON” position and the accelerator pedal is not depressed. Anti-Rolloff is
deactivated when the key switch is in the “OFF” position When the key switch is in the “ON”
position and the truck is stationary, the controller supplies a small current to the field. This
current is used to sense if the armature is rotating. As the armature begins to rotate, the
controller senses a fault condition and then supplies current to the field opposing the armature
rotation, slowing the vehicle.
Refer to Motor Specifications Table for information on the maximum allowable field current
when the Anti-Rolloff feature is active.
To test the Anti-rolloff feature:
Park the vehicle on a flat level surface, turn the key switch OFF and apply the parking brake.
Connect an analog Ammeter in series with the motor field windings or a clamp on Ammeter on
one of the field wires that is capable of reading up to 25-Amps.
Place the forward and reverse switch in the center OFF position and turn the key switch ON
TEST #8.1
Read the motor field current on the Ammeter.
If the field current is greater than specified in the Motor Specification table (see Motor
Service section for specifications), then the Anti-Rolloff feature has failed. Check the
status of the Anti-Rolloff feature using the hand held calibrator (62-027-61).
TEST #8.2
While monitoring the motor field current, release the park brake, and push the vehicle.
Within approximately 10-feet, the field current should rise dramatically and the vehicle should
become difficult to push. Now stop pushing the vehicle and allow it to come to a complete stop.
The field current should drop down below the value specified in the Motor Specification table.
This indicates that the Anti-Rolloff feature is operating normally.
If the current does not rise, then the Anti-Rolloff feature has failed or has been turned
off.
The status of the Anti-Rolloff feature can be checked with the hand held calibrator.
If the Anti-Rolloff feature is on and the field current did not rise, then the controller has
failed and must be replaced.
If the Anti-Rolloff feature is off then the controller logic must be reprogrammed. Contact
your dealer.
The surface must be level for this test. Do not attempt to test the
Anti-Rolloff by pushing up or down an incline. Testing by pushing up
or down an incline could result in injury or property damage.