Excel 800 Troubleshooting
77 EN1B-0375GE51 R0910
I/O Modules Troubleshooting
► Check if the power supply voltage level is OK and that there is no high voltage (> 24 VAC or > 40 VDC) connected to the
inputs/outputs of the …821, …822, …823 I/O modules.
► Replace the problem I/O module with another module of the same kind.
– If the problem persists, this is an indication that the problem is caused by the application or incorrect wiring.
– If the problem is solved, this is an indication that the I/O module was defective.
For troubleshooting purposes, the following features can be used:
Power LED (all Excel 800 I/O modules)
Service LED (all Excel 800 I/O modules)
Service button (pluggable I/O modules, only)
In addition, a module-specific troubleshooting may be necessary.
Power LED of I/O Modules
case Power LED Meaning Remedy
1 ON
I/O module is powered.
No action necessary.
2 OFF
No power.
► Check power supply.
3 Flashing continuously
If the I/O module’s service LED is likewise
flashing, the I/O module is in the boot mode.
► Wait until rebooting (firmware
download) has been completed.
Table 77 Power LED of I/O modules