SLC 5/01 Stuck Runtime error Help needed

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A "Stuck" Runtime error is detected on I/O module 3
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In a System comprising: SLC 5/01 CPU / 16 Input DC Sink / 8 Output Relay / Analogue Output, Modules (1 of each in that order)

We get the above fault, also noted:
Major Error Halt S:1/13 Flag=1, (all other flags=0)

This fault has been occuring on the PLC for the last 3 years about once every 2 month. We connect RSLogix, clear the fault. Then the machine is running again.

With regard to making a permanent repair can anyone advise the cause or where I should be looking?

thanks

micgent

Make sure all digital outputs have surge protection.

No actually there is a better way to isolate what the real problem is

Get a copy of the SLC 500 instruction set look up the error corrections recommended under s:1/13 and s:6 the exact error can be recorded by following the instructions provided under the s:6 status bit it will provide a hex value depending on what error occured also I beleive s:20 and s:21 also provide some insite but check that under the s:6 heading in the instruction set. Also you can clear this with the keyswitch by toggling from program back to run or set s:1/8 to 1 clear major errors on power up