Went on a service call this morning for red lights flashing on a plc and no io working.
I went into the plant and tried to upload the program, it said no program was in the plc
When I look at the manual for why those lights are flashing it said it needed firmware update, so I updated firmware and downloaded a copy of program that I had and everything worked.
Anybody have any idea why the plc lost its program in the first place everything I looked up said this plc doesn’t have a battery so but it saves memory it self and the mem save light was always green on the plc which manual says that means it’s saving the program
It sounds like you encountered a frustrating issue with the PLC losing its program. Since you’ve already confirmed that this model doesn’t have a battery and relies on internal memory, the issue could stem from a few possibilities:
Firmware Bug: It’s possible the older firmware had a glitch that caused the program to be lost, especially if it was corrupted during a power cycle. Updating the firmware, as you did, was the right move and may prevent this from happening again.
Power Interruption: Even if the memory save light was on and indicating normal operation, a sudden or improper power shutdown might have affected how the PLC saved the program. Some models have a capacitor or a non-volatile memory that could degrade over time.
Corrupt Program File: If there was a corruption in the program file stored in memory, it might cause the PLC to clear it or fail to recognize it, leading to the “no program” state.
External Factors: Sometimes electromagnetic interference (EMI) or grounding issues can impact the integrity of stored data, though it’s a bit more rare in modern systems.
Since the firmware update and re-upload of the program resolved the issue, it’s worth monitoring closely. If it happens again, it could be a deeper hardware issue with the PLC’s memory
