MicroLogix 1400 Intermittent 0379h Fault

[almosttechy]

Hi everyone,

I hope I don't butcher this up, please feel free to critique me wherever if I do, I have an issue I would equate to "chasing ghosts."

We have a few processors that are throwing a 0379h fault back to the processor. My understanding is that this is a major fault at the third expansion module (which is a thermocouple module in our case.) This is happening on multiple units randomly. We are unsure what the root cause is and why it is happening across multiple processors. The fault can be cleared and things go back to normal temporarily; then it may come back on any of the processors. Rockwell suggested that we update our firmware. Any other suggestions for areas to start troubleshooting would be greatly appreciated.

 

[tarik1978]

You have to check the I/O module status file (IOS), it could be open circuit, overrange, underrange error or the CJC ( cold junction compensation) error.

 

[almosttechy]

Sorry for the follow up question, how would I check the I/O module status file? Would that be found in RS Logix 500?
I'm new to this stuff, again apologies.

 

[almosttechy]

Okay, this looks like a "general hardware issue, no additional information" situation from the extended fault info. X300.... Where in this good green earth would I even start with that? This issue isn't localized to just one PLC. We have four that all have this issue and they are all brand new.

That said I don't feel inclined to just replace a bunch of T/C modules since all 4 of these for each of the 4 lines is new. I guess we could look into another temp controller. I wonder if this is a problem with the 1400 processors or if there's some weird noise or power issues happening.

 

[OkiePC]

Are you using grounded thermocouples with those modules? I rarely have used the T/C module with a 1400, but have encountered issues with other modules that often ended up being caused by noise getting back to the card via grounded thermocouple tip.