slc5/04 faulting out

i have a plc that in the last four months has faulted out three times a month on anverage. in the fault screen it always shows the same ladder and rung where the fault occured which is ladder 2 rung 18 which happens to be the end statement on the ladder. resting the fault the plc will exicute the program once and fault again same place reloading the program and it goes away for a few days or weeks. any suggestions?

Hi Harry,

when the SLC5/04 faults the next time, go online and check the system status word S:6 (Major error fault code) and S:5/0 (math overflow trap).
These will help you to determine the cause of the fault.

By the way: that the fault is always in the last rung of the program could indicate that it is a math overflow.
To get past this problem: In the last rung of the program put an unconditional unlatch of S:5/0. In the rung before the last rung you could put an evaluation of S:5/0 that generates an errormessage such as "math overflow in program".
I suggest that you implement this right away without waiting for the next fault.

good luck,