PILZ PNOZ X4 Safety Relay

[fadi90]

Hi everyone,

I'm working on repairing a Pilz PNOZ X4 safety relay module. When I opened it up, I found some of the connector pins detached from their pads. I replaced the connector with individual wires, but the issue remains.

The module is set to dual-channel mode with manual start. In this mode:

• Y36-Y37 and Y1-Y2 are bridged.
• 24VDC is applied across A1-A2.
• It monitors two emergency circuits (S11→S12 and S11→S52).
• When both are closed (24V present on S12 and S52) and the start button is pressed (S33 connected to S34), the NO contacts (13-14, 23-24, 33-34) should close.

In my case, although 24V is present on S52, the CH1 LED doesn't turn on, and the contacts don't close. It's behaving as if S52 isn't getting power, even though it is.
I compared it with a working X4 safety relay and found that one of the internal relays isn't receiving a ground signal.
I switched some elements between both working and nonworking boards, nothing changed.

I'll provide a photo of the faulty board here, more in a google drive folder. Any help identifying possible causes or failure points would be appreciated.

Thanks in advance!

[Per Hansson]

I would not repair a safety relay: if it fails and someone dies/gets injured and your where the last one working on it that would turn into a lawsuit.
Safety relays are cheap, just replace it with a new one.