Taylor-Dunn ET-015-00, Operation, T Roubleshooting And Replacement Parts Manual

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Maintenance, Service, and Repair
Electrical Troubleshooting
Page 10
Contactor Negative Return
The forward and reverse contactors coils use a common negative return that is provided by the
controller from Pin #3. The negative output from Pin #3 is part of a fault monitoring circuit in the
controller. If the controllers senses a short circuit in the controller output, it will not provide a negative
signal to the contactor buss preventing the contactor from closing.
Disconnect the Green power cable from the controller M- terminal.
Connect a test light from the controller M- terminal to the B+ terminal.
Connect a test light from the contactor negative buss to the B+ terminal on the controller.
NOTE: MUST USE TWO TEST LIGHTS!
Close the seat interlock switch and turn the key switch ON.
> The test light connected to the contactor negative buss should be ON.
> If the control system is working, the test light connected to the M- terminal should
vary in intensity depending on the position of the throttle pedal.
Negative buss test light is ON: Controller fault circuit working.
Negative buss test light is OFF: Perform tests at Controller Small Signal Input. If all good
then replace the controller.
Repeat the test with the Green wire reconnected to the M- terminal.
> If the test fails with the wire connected but passed with the wire disconnected,
then there is a short in the vehicle power wiring or motor.