IC200MDL742 Digital Output Module

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When I Switch off My main circuit breaker for the 24VDC for the PLC panel, I still have 24VDC supplied loads remain ON, when all are supposed to be off. I measured across terminals 17 and 18 of the Digital Output Module - IC200MDL742 and am getting 24VDC even with my power supply switched off.

This is giving me PLC network error. 

Am I supposed to be getting that 24VDC across terminals 17 and 18 of the module even with the power supply switched off?


thank you,

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Terminals 17 and 18 are for the external supply required to power the outputs. If it is still showing voltage after you turn off a breaker, it sounds like that breaker doesn't interrupt all DC power. You need to check the wiring diagram for your system to find the supply for those terminals. 

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Thank you so much Steve Bailey.

I checked through the wiring and found that +24VDC was present at terminal 18 through one of the digital outputs on that same module to a field device. I am in the process of locating that field device. This is a fairly old plant that I am working in and much of the information like electrical schematics are no longer available.

This is happening in one of the five Remote I/O panels for GE Versamax, all linked via Profibus Network Interface.

I isolated that particular discrete output and the 24VDC circuit breaker now effectively interrupts all DC power supply. Seems that this particular output was back-feeding the module which must have damaged the output module. 

With this issue isolated, the network fault LED on the Profibus Network Interface module is now solid Green, i.e. healthy.


Thanks a lot Mr Steve Bailey.

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