S7 414-3 Problem when power is off

Hello there,

So, on a few of our machines, we have S7 414-3 with a UPS system to keep them up for 24 hours our if the power is off. Sometimes we are shutting down the power for more than 24 hours when we are making planned repair or renovation.

The problem is following - sometimes (not always) when we turn the PLC on again, all the lights start flashing but the PLC doesn't start. The first time we fixed it with repeatedly restarts and got fixed after a few. Also, I noticed that if I remove the batteries and then put them back and download the EPROM again it got fixed instantly.

Is that a known bug, does somebody else have it? Maybe there is a firmware update or something?


Thank you in advance

Dear D.st,

Please tell us the model no of your memory card using in the CPU?

Also when do you face this issue? Just after when you shut down your power more than 24 hours and your backup ups is also down?

According to the last line you wrote i assume that you have a FLASH memory card not SRAM.

Yes, it's only when the backup power is also off. 

The memory cards we use are F-EPROM for S7 400 - 6ES7952-1KL00-0AA0