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Electrician Red Seal · Question

A technician is troubleshooting a PLC-controlled conveyor system. The 'Conveyor Start' push button is wired to input I:0/0 and the 'Motor Run' output coil is O:0/0. The PLC program has a line of ladder logic: `LD I:0/0, OTE O:0/0`. When the operator presses the start button, a multimeter across the motor contactor coil terminals reads 0 V, and the motor does not start. Assuming the motor contactor and wiring from the output are good, what is the most likely issue?

If the multimeter reads 0 V across the motor contactor coil terminals, it indicates that the PLC output O:0/0 is not energizing, preventing power from reaching

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Question: A technician is troubleshooting a PLC-controlled conveyor system. The 'Conveyor Start' push button is wired to input I:0/0 and the 'Motor Run' output coil is O:0/0. The PLC program has a line of ladder logic: LD I:0/0, OTE O:0/0. When the operator presses the start button, a multimeter across the motor contactor coil terminals reads 0 V, and the motor does not start. Assuming the motor contactor and wiring from the output are good, what is the most likely issue?

Answer options:

  • The PLC input I:0/0 is stuck ON. ✅ The PLC output O:0/0 is not energizing.
  • The conveyor motor is overloaded.
  • The Stop push button is active in another part of the program.

Correct answer: The PLC output O:0/0 is not energizing.

Explanation: If the multimeter reads 0 V across the motor contactor coil terminals, it indicates that the PLC output O:0/0 is not energizing, preventing power from reaching the contactor. An overloaded motor would typically draw current but the contactor would still be energized. A stuck ON input or an active stop button would be programming issues if the output was already trying to energize.

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