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Logix Controllers with Solid Red OK LED

Wayne Welk9/21/2018

What to do when your Logix controller is inoperable with a solid red OK LED status indicator? At first it may appear that this is a non-recoverable fault condition, but there are a few steps to try to clear the fault and get operational again.

The steps below from from Rockwell Automation’s Knowledgebase AID 43329 (login and TechConnect required to view this KB article). 

Below are two charts from the ControlLogix® System User Manual that describe the state of the controller based on the OK indicator. Typically a flashing red OK indicator is a sign of a major fault and is usually recoverable – meaning that the fault can be cleared using RSLogix 5000 or Studio 5000 software. A solid red OK indicator, may be a clear sign that the CPU is inoperable and needs to be repaired or replaced.  But in some circumstances, a solid red OK status may be able to be recovered. Provided below are the suggested steps to attempt to recover from a solid red OK indicator. 

If the controller is a ControlLogix, CompactLogix™ or a Flex Logix™ processor, try powering down and removing the battery or ESM to bleed off memory (CompactLogix is recommended to be powered down for more than 45 minutes). If the OK LED remains solid red, then the controller became inoperative for some reason and will need to be replaced or sent in for repair. 

When the OK indicator is solid red, one of the following is true: 

  • The controller is completing the power up diagnostic. 
  • The controller is powered, but is inoperable. 
  • The charge of the capacitor in the ESM is being discharged upon power down. 
  • The controller is loading a project to nonvolatile memory. 

If the “OK” indicator is solid red and persisting, then try one of the below procedures to clear the fault: 

  • Make sure the power supply input voltage (120V AC or 240V AC) setting is appropriate (Check Expansion bank I/O Power supply can cause the Controller Solid Red on Power UP). 
  • Cycle the power of the controller and check the status. 
  • Remove the controller from the chassis and place it in again, then check the status. 
  • Remove all the cards except the controller from the chassis then power up and check the status. 
  • Clear the memory on the controller using the steps in 450803 – 1756-L7x:Clearing memory/Resetting processor to factory default, then re-download to the controller. 
  • Clear the memory on the 1756-L8x and 5069 controller using the steps in 766058 – Clearing Memory of 1756-L8x & 5069 Logix Controllers, then re-download to the controller. 

If the fault condition still persists, then the Logix controller is inoperable and needs to be replaced or repaired.