28    CompactLogix Controllers 
Publication
 1768-IN004D-EN-P - December 2009
Troubleshoot System Power
The CompactLogix power supply works with the CompactLogix 
controller to provide power to the system. You must consider both 
when attempting to troubleshoot system power.
To troubleshoot system power issues, use the CompactLogix power 
supply PWR status indicator and the CompactLogix controller PWR 
and I/O PWR indicators. If the power supply is not operating 
properly, the controller will not operate properly either. You must 
first diagnose and correct any issues with the power supply before 
troubleshooting the controller.
1. Examine the power supply PWR status indicator.
2. If the power supply is operating properly and the power 
supply PWR status indicator is green, examine the controller 
PWR indicator.
3. If the controller PWR status indicator is green, examine the I/O 
PWR status indicator.
IMPORTANT
Before you disconnect, reconnect, or replace any component, make sure you 
have turned off power and allowed all system status indicators to turn off.