What would cause my L63 PLC to lose "RUN" status? 1

[MHadley]

I was called in because our machine went down, operators could not control the PLC equipment for Drives through the DCS system. Found a PLC rack with all IO and comm modules faulted but the controller was not faulted. The controller IO and Run status lights were off.

Cycled the power to the rack and turned the L63 key from Run to Rem and back again. This fixed the problem. I still have to figure out what may have happened. I cannot keep the machine down to try to recreate the problem at this time. I am looking for suggestions as to what I might check on my next opportunity. It happened once, it is likely to happen again if I can't find the issue.

I think if the rack lost power, this could cause this scenario...I checked the wiring and don't see any defects. Maybe the power supply is failing??

Any help that is offered is appreciated.

 

[automatic2]

what does your error history report?

 

[controlsdude]

More than likely if you have a rack fault the processor stops, if they set the IO up to stop the processor, which would be a good idea. Because if you just let it run with faulted hardware you get that undefined state and weird things happens, like a machine crash.

Probably a flakey power supply on the rack that was faulted. If there was an IO problem the IO Light on the processor would be blinking. This tells you that hey look at the code, something is wrong. IO blinking = failed hardware on the IO config tree.

best break out the laptop hook up to the machine find your problem. do all the simple stuff first usually finds 95% of the problems.

 

[bgrice33]

Hi there,

I agree that you could have a rack issues. I would also check that you power is clean and the ethernet. Once we had an issue where someone was attempting to get onto a processor remotely and once they did it put the processor into program mode. Also is what does the error messages say in the processor?
Link

 

[MHadley]

Thanks to all for the great advice. I will see if there is anything in the error history.