You are not registered yet. Please click here to register!

plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!

Go Back - Interactive Q & A > - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Thread Tools Display Modes
Old December 6th, 2017, 04:22 PM   #1
United States

snakes79 is offline
Join Date: Nov 2015
Location: Illinois
Posts: 9
Intermittent fault AB -- L24ER-BB1B

Hello friends. I have a PLC in the field that intermittently faults out. Its a compact logix L24ER-BB1B. The status "OK" light blinks red, according to the customer. He toggled the switch from program mode to remote, to reset the fault, and the machine resumed operation. According to the customer, this has happened 2 or 3 times in a month.


Does toggling the switch erase the controller fault list in the properties window?

Has anybody ever dealt with something like this?

If there was a negative number in a counter or timer, (which I don't think happened) Toggling the reset wouldn't fix the problem, and it would fault out again instantly?


  Reply With Quote
Old December 6th, 2017, 04:48 PM   #2
Supporting Member
United Kingdom

janner_10 is offline
Join Date: Dec 2014
Location: Tewkesbury
Posts: 696
You need to go online and see what the fault is.
  Reply With Quote
Old December 6th, 2017, 08:24 PM   #3

Jeev is offline
Jeev's Avatar
Join Date: May 2008
Location: Brisbane
Posts: 453
Does this site have a lot of brown-outs, supply transients or do they have a habit of cycling power to fix things often?
  Reply With Quote
Old December 6th, 2017, 08:59 PM   #4
United States

GaryS is offline
GaryS's Avatar
Join Date: Aug 2003
Location: Lancaster Pa.
Posts: 852
The Micrologix and SL line will do that with a math overflow fault just going to program and back to run will reset it until the next time.
I don't know if the Logix processors still have that problem
  Reply With Quote
Old December 7th, 2017, 10:11 AM   #5
United States

ScottTheEngineer is offline
ScottTheEngineer's Avatar
Join Date: Sep 2006
Location: SE Michigan/NW Ohio
Posts: 142
I had a couple that did that do to programming error. The SCP instruction I was using had indirect addresses and I was causing a divide by 0 error When I accessed the routine they were located in.
  Reply With Quote
Old December 7th, 2017, 12:12 PM   #6
Ken Roach
Lifetime Supporting Member + Moderator
United States

Ken Roach is offline
Ken Roach's Avatar
Join Date: Apr 2002
Location: Seattle, WA
Posts: 14,418
The ControlLogix/CompactLogix OS considers overflow and divide by zero to be minor faults, which will not stop the user program.

An out-of-bounds array index will definitely fault the controller, and that's the sort of thing that's very typically reset during an initialization routine.

I agree that OP needs to go online and look at the fault logs. I admit I don't remember if they are cleared by a keyswitch cycle or power cycle.
  Reply With Quote
Jump to Live PLC Question and Answer Forum


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
AB Kinetix 350 MCCM Instruction Execution Intermittent Direction Change dfreerks LIVE PLC Questions And Answers 1 June 11th, 2014 05:09 PM
Fault & restart AB SLC 5/04 periodically Ffakury LIVE PLC Questions And Answers 11 February 4th, 2014 05:22 PM
AB PLC 5 Processor fault mureed LIVE PLC Questions And Answers 3 March 13th, 2011 08:10 PM
AB PLC5/80B RIO Flex IO Fault corkers LIVE PLC Questions And Answers 9 September 4th, 2004 02:12 AM
Ab Plc5 Rio Adapter Fault Simil LIVE PLC Questions And Answers 4 July 25th, 2003 10:27 PM

All times are GMT -5. The time now is 08:37 AM.