What is the next step if an input PLC indicator light is off when it should be on?

When the input PLC indicator light is off and it should be on, one of the first steps in troubleshooting is to check the wires for an open. An open wire condition can prevent the proper signal from reaching the PLC, which leads to the input indicator not lighting up when it should. This step allows you to verify that there is a continuous path for current to flow from the input device to the PLC. If any wire is damaged, disconnected, or broken, the signal will not reach the PLC and the indicator light will remain off.

Inspecting the wires for any signs of damage or disconnection is essential, as this is often a common issue in troubleshooting PLC inputs. Ensuring the integrity of the wiring can help ensure that electrical signals are transmitted properly, allowing the PLC to function as intended. Additionally, checking the wiring is generally a straightforward and preliminary step before considering more complex or costly solutions, such as replacing the PLC or resetting it, which may not address the root cause of the issue.