Hi,

We have received one alarm in our AB PLC (PLC-5 Processor 1785-L40C15)
'Adaptor # 3 Fault' and persisting in alarm page. In the Adapter # 3 (1794-ACNR15)all
the LEDs are healthy. (COM A&B, Status LED are green and steady)
Our system is redundant system, processor and all the IOs,
Node 3 is main and Node 4 is redundant.

After receiving this alarm some of the solenoid-operated valves are not operating
properly in auto sequence because the valve feed backs are not changing in the data table.
Toggle the signal from Ladder logic, valve is operating, feed back signals from the open
close limit switches are changing and verified in the Digital input module, field status is
matching but in the data file it is not changing.

ie. open condition open signal = 1 close signal also showing 1
but close condition close=1 and open=0

Is it Adapter fault or any other fault? Becoz the LEDs

Is it safe to change the Control net redundant adapter on line ?

Rest of the process is running well except the NODE 3 & 4

Kindly give your recommendations to solve this problem.

Thanks in advance.

Joy

I am just swagging here as I have not worked with pure PLC 5 Controlnet, but it sounds like your 1794-acnr15 has detected some fault either in itself or the assocaited I/O modules.

Have you tried resetting the fault? A power cycle comes to mind.

I have seen with 1771 PLC I/O where the I/O module LED would show the input true but the data table would not match the led state. This was caused by a failure of the input to backplane opto isolator and was resolved by changing the I/O modules.

If the inputs that are not responding are on a single I/O card I'd change that card, if they are on multiple I/O cards then I'd try another 1794-acnr15 adapter.

Just some random thoughts to get you started until others with more PLC 5 Controlnet experience respond.