S5 95U randomly STOP then RUN again

Hi All,

We have a hydraulic press that is being controlled by Siemens S5-95U PLC . Lately the S5-95U has been randomly stopping during operation thus causing the hydraulic press to stop running. However the S5-95U instantly returns to RUN status after stopping. This is the first time it has happened after a decade of service.

Prior to the random stops issue, around January 2021 the S5-95U completely stopped and the program in the RAM was erased so we had to replace the PLC battery and restore the program with our backup. Strangely, the PLC battery we replaced still had 3.4VDC upon checking. What's even more baffling is that even after we replaced the PLC battery with a new one, Battery LED is still yellow although the program is still retained in the RAM.

In summary, we have two concerns:

1. S5-95U randomly stops and resumes during operation ever since we were forced to replace the PLC battery and restore the program.

2. PLC battery has been replaced but the Battery LED is still yellow but the program is still retained in the RAM.



I have a suspicion that the two concerns I mentioned above are somehow connected but I lack the technical expertise to diagnose. I'm hoping someone can help me figure out our issue. Worst case, I think our S5-95U needs to be replaced.

https://imgur.com/gallery/iOQwnfy

Thanks,

First of all, I noticed it does have extension I/O, this can be a source of problems, the connectors get tarnished or dry joints on the boards where the connectors go, sometimes removing them & plugging them back in cures random drop outs, as for the battery, it sounds more like the is a probable fault in the battery circuitry rather than the battery, although you are correct both faults could be related, I do suggest you replace the system, S5 is long past it's usable date and probably worth upgrading.

Good news is that you should be able to get the program out because its not dead yet... make sure you get a cable and the software and upload the program so you have a back up

Bad news is they stopped making them in 2012 so your best bet is find one on ebay, looks like you have a eprom so it should be an easy swap, but I stress SHOULD be easy

They have 89 on ebay... a word of caution, they show new factory sealed in China, these are not new they are used/refurbished and put in a new box

If the battery is indeed new, then the CPU has an internal problem. I would either replace the 95U, or upgrade to S7-1500, which would mean replacing the HMI as well, if applicable.

Why even bother with keeping an S5 alive? Are you going out of business next week?
If your company is planning to stay in business, upgrade that PLC.

if you replace the plc, install a surge suppressor if on is not already installed.
i like corcom brand.
james