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I am using an E10-npn+ PLC with inputs 1 & 2 connected in parallel. While on-line monitoring, input 1 is always being on regardless of the status of the hardware. I can see activity, green LED, at the input but no control of the outputs. While simulating the same program, all is OK. That is, I can toggle the inputs and get the correct outputs. I moved the hardware switch from input 1 to input 6 and changed the program accordingly, and it worked OK. I tried two new PLCs and the same thing happened with both. Could input 1 be defective on the PLC board? Please advise.