Siemens SIMATIC NET S7-300 - Possible Sources of Problems and How to Deal with Them

5.1 Possible sources of problems and how to deal with them
Fuses
Note
The CSM 377 compact switch module has a resettable fuse / PTC. If the fuse triggers (all LEDs are
o󹪜 despite correctly applied power supply), the device should be disconnected from the power
supply for approximately 30 minutes before turning it on again.
LED display when voltage drops
If the power supply sinks below approximately 14 V, the internal power supply switches o󹪜, the
L-LED and all port LEDs go o󹪜. The functionality of the CSM 377 is no longer available.
Device defective
If a fault develops, please send the device to your SIEMENS service center for repair. Repairs on-
site are not possible.
Maintenance and troubleshooting
5.1 Possible sources of problems and how to deal with them
Compact Switch Module CSM 377
34 Operating Instructions, 06/2022, A2B00073499-02