It was the old 8 bit input module - light came on but the processor wasn't recognizing it. We figured this out after upgrading to a PLC-5 and going online. Maintenance tells me they had previously swapped the module, but they tell me so much stuff I don't know what is really true.
Of course, we had to go to a PLC-5 because maintenace also determined that the PLC-2 processor was bad so they ordered another before I could borrow our local distributor's laptop with the PLC-2 software. Well, in swapping the PLC-2 processor, they managed to fault the processor, loose the program, and break multiple pins off the EEPROM. The only electronic copy of the program was on tape at the machine supplier who was unable to read it. Coupled with the fact that we had no cables or software for the PLC-2, I bit the bullet and re-entered the program by hand into RSLogix 5.
At least now we are more capable of supporting this platform in house.
There is one other mechanical problem that is now being attributed to a maintance guy standing on some valves to replace a bearing before this all started. They are swapping valves now and hopefully this will get the machine back up.
I doubt I'll ever know the full story of what all happened before maintenance asked for help.
