1769-L33ER troubleshooting

Hi everyone,

I am looking for help for the 1769-L33ER pl .

The issue I was facing is the PLC OK LED was solid red. I read that this was an unrecoverable fault so a new PLC was purchased but when installed had the same RED LED fault.

The PLC and IO is installed over two racks.

The first rack contains the PLC a 1769-PA4 power supply and 6 digital input modules. This is connected to the second rack via a 1769-CRR3 module extender.

The second rack has two analog outputs, two analog inputs and two digital outputs then a 1769-PA4 power supply with a left hand terminator.

This is where it gets interesting, if I disconnect any of the modules on the second rack then the RED LED goes away replaced with a flashing red ok led and a flashing IO led. If I connect the module again the flashing red ok led becomes solid.

I have tried to move the bottom power supply along the line skipping the IO on the bottom rack but with no success.

Does anyone have any ideas?

I am starting to think maybe it's the module extender but I don't know for sure.

Any help would be much appreciated.

I cannot see your pictures. What is the layout of your rack? Usually, You can have the processor and 3 additional modules to the left of the first power supply, and then 8 modules to the right. There are some specially modules that have additional requirements. On the 2nd and 3rd rack, you can have 8 modules on both sides of the power supply.

The best way i know to troubleshoot compactlogix issues like you have is start at the end of your addon cards and remove the cards one at a time, replacing them with the end cap. That should tell you where the issue is.

Helliana said:

I cannot see your pictures. .

Click to expand...

Try making the pictures smaller

calvindodds said:

This is where it gets interesting, if I disconnect any of the modules on the second rack then the RED LED goes away replaced with a flashing red ok led and a flashing IO led.

Click to expand...

Try power down removing all cards, does it boot? yes add one card at a time and try again or remove the terminals to see if there is a short in the field, no then remove the power supply

I hate doing it but the fastest way is just plug and play to see if the fault clears

after you go to online in RSlogix, it will show faulted, open property then select major fault tab, there should have more detail info about this fault.

mike3475 said:

after you go to online in RSlogix, it will show faulted, open property then select major fault tab, there should have more detail info about this fault.

Click to expand...

Maybe... but odds are if its a solid red light you won't be able to go online until everything is cleared and reset and then the fault is gone