0071h fault on Micrologix 1400

Steve Jackson

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May 2016
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Indiana
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I have a fault that shows up periodically on two different Micrologix 1400 PLCs I have controlling 45A (5 watt, 120 Volt) series Mac Valves. There are 12 Mac valves in the system all turning on with different PLC outputs, but at the same time. The Mac valves then turn off after "x" amount of fill time, each output is not turning off at the same time. The PLC outputs are wired to a 1762- OW16 expansion card. I have the 0071h fault show up sometimes 1-2 per day, sometimes not at all. The fault is easily reset by changing to PROG mode and back to RUN mode. I have read that the fault is a communication problem with an expansion card. I have also seen in some older forums that surge suppressors could be used for the outputs, but is the solenoid current draw enough to make the relays in the output card fail?

Any thoughts from the group on what you have seen/done? 🍻
 
I changed out all 1762 expansion cards one at a time and finally the Micrologix 1400 to remedy this problem last year. The expansion card changes did not correct the problem only the PLC did.
 
I have also seen in some older forums that surge suppressors could be used for the outputs, but is the solenoid current draw enough to make the relays in the output card fail?

If you don't have snubbers on your solenoids, you're asking for failure inside 2 years on a typical installation. The spark created by back-EMF eventually wears out the contact surface and allows it to stick, rather than welding the contacts together like an over-current event does.

The first thing to do is to improve your grounding of the controller. Go find the ground wire and double its size.
 
The first thing to do is to improve your grounding of the controller. Go find the ground wire and double its size.

I can check this later in the week when the machine is down. Thank you.
 
If you don't have snubbers on your solenoids, you're asking for failure inside 2 years on a typical installation. The spark created by back-EMF eventually wears out the contact surface and allows it to stick, rather than welding the contacts together like an over-current event does.

The first thing to do is to improve your grounding of the controller. Go find the ground wire and double its size.

I found that the SMC solenoids without the surge suppressor created a lot of random issues with the outputs in the Micrologix. Once we made sure all of the solenoids we ordered had the suppressor installed the problems went away.

The grounding and snubber suggestions should fix him right up!
 
Ground wire is a 14 gauge wire. I have secured all connections of the ground wire. Snubbers for the 120 Volt solenoid valves have been ordered.

Is it possible if my incoming power is not a constant 120 volts, that i could get the 0071 faults? I have ordered a Sola CVS to regulate the incoming 120 Volt power.
 
While I also don't like the sound of the output handling here, and would also advocate implementing good practices, which you now appear to be working towards; I would also like to rule this in or out...

Steve Jackson said:
I have a fault that shows up periodically on two different Micrologix 1400...

...I have the 0071h fault show up sometimes 1-2 per day, sometimes not at all...

...The expansion card changes did not correct the problem only the PLC did...

What FRN (Firmware Revision Number) are these MicroLogix 1400 controllers at? There was a known anomaly with certain FRN 3 or older configurations which upgrading to FRN 4 (or newer) seemingly resolves...

56882 - MicroLogix 1400 and error code 71h with a 1762-OF4 or 1762-IQ16 installed in the first expansion slot
Access Level: TechConnect

Regards,
George
 
Ground wire is a 14 gauge wire. I have secured all connections of the ground wire. Snubbers for the 120 Volt solenoid valves have been ordered.

Is it possible if my incoming power is not a constant 120 volts, that i could get the 0071 faults? I have ordered a Sola CVS to regulate the incoming 120 Volt power.

I had a similar issue with a SLC-5/04 and 120v Relay Outputs firing hydraulic solenoid valves. Occasionally I would get a communication fault on that slot, which we could easily fix by turning the key like you mentioned earlier.

I ended up installing isolation relays between the card and the valves and this resolved the issue. Still has the same output card on the PLC. I honestly think the surge suppressors you ordered will do the trick.
 
Steve Jackson said:
FRN number is 3.0

That is interesting. Both offending MicroLogix 1400 controllers are at FRN 3?

Can you access the Rockwell technote I linked earlier? You do require a TechConnect Contract to view it, but it doesn't really matter as I've already mentioned that flashing the FRN to 4 or higher is apparently the fix for this very specific anomaly.

In case you are not already aware, and you wish to attempt a controller FRN upgrade to resolve your issue, here are the specific instructions to do so...

36290 - How to update firmware on MicroLogix 1100, 1200, 1400 and 1500 controllers
Access Level: TechConnect

That also, surprisingly, requires a TechConnect Contract to view it. Why TechConnect is required for simple controller firmware flash instruction, I do not know? If you cannot access it and you'd like to know more on the flashing procedure then do let us know.

p.s. At FRN 3 I believe your MicroLogix 1400 controllers would be Series A hardware. If so, then the only Series A firmware available for download is FRN 7, which is the latest they support and would achieve the maximum FRN upgrade possible here and help eliminate many anomalies that would have been addressed since FRN 3.

Regards,
George
 
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I seem to be having trouble with my Tech Connect account. I cannot access the post you have listed here. Can you please post it on the forum page?

I can see another link in Knowledge base about having a IQ-16 in the first expansion slot. I can not open that document either, but I do have this input card on both machines that I am having trouble with.
 
Ok. I have my Tech Connect working properly now.

I have a 1766-BXBA Micrologix 1400 and a 1766-BWAA Micrlogix 1400 that I will need to update the firmware on. The versions are from 11 to 21. I am not sure which version to start with.

I have attached a screen shot from the Status files for reference.

Micrologix 1400 1766L32BXBA.jpg Micrologix 1400 1766L32BWAA.jpg
 
I downloaded Version 11 earlier through Rockwell. I am fine with using Version 12 or whichever one will work. My RSLogix 500 is Version 9, so that would need to be considered.
 
Ne'FRN'ding confusion?!?...

Mickey,

Steve is referring to firmware revisions 11 - 21, not RSLogix 500 software versions, which we are viewing in your screenshot. For the software, v11 is the latest and greatest - there is no RSLogix 500 v21, of course.

Steve,

I can't quite make those out but it looks like for the hardware levels they are both at OS Series B & Processor Series B?

I also can't quite read the OS FRN but there seems to be three digits for each, suggesting at least FRN "10.x" or higher? Maybe a "15.x" for one of them? My eyesight is only so good, as are your screenshots.

The Processor FRN looks to be "3.0" for each, yes? I think this is what you have been relaying back to me?

Can you improve on the screenshots or just type in all the details here please?

Either way, if the hardware is indeed Series B, then you are correct on the FRN available to flash these controllers...

MicroLogix Series B: FRN 11.000 - 21.003

But...

I feel you were a little mixed up in which "FRN" I, or more, the technote was referring to? The Processor FRN 3.0 is fixed. It is the OS FRN that is updated with the different revisions of controller firmware and it is this FRN which I/technote was referring to as possibly being at FRN 3. Because I thought you were quoting "FRN 3.0" as OS FRN 3, that is why I assumed you had Series A hardware...

Series A: OS FRN 3 - 7
Series B: OS FRN 11 - 21
Series C: OS FRN 21

The Processor FRN 3 does not change and has thrown you/me off here. But you wouldn't be the first to be confused with these numbers...

For earlier MicroLogix 1400 Series A controllers, they would have been initially released with both OS FRN 3 and Processor FRN 3 at the one time. As updated OS FRN were released, i.e. controller firmware updates, the OS FRN has gradually incremented over the years, while the Processor FRN remains at 3. This OS FRN incrementing also carries through the different Series hardware releases, with Series A hardware only supporting OS FRN 3 - 7. The introduction of Series B hardware then jumped and started at OS FRN 11 all the way up to the latest OS FRN 21. Series C hardware, introduced last Summer, only supports the very latest OS FRN 21 and cannot be flashed with any OS FRN lower than that.

So, you might ask - what is with the OS (Operating System) FRN really meaning the processor firmware, as we normally refer to it, and the Processor FRN, well meaning what? The Operating System refers to the firmware that the processor uses to run programs. The "Processor FRN" refers to the "BOOT FRN", somewhat like the BIOS in a computer system. It is what the controller uses to BOOT each time is it powered on, and before loading the OS FRN. When you are flashing the OS FRN, it is used to handle the flash and the transitional period in between firmware revisions. It would have made more sense to just call this "BOOT FRN", or not even expose its existence to users at all.

Here are screenshots of before and after an ML1400 OS FRN flash...

ML1400%20Series%20B%20FRN%2015.2.bmp

ML1400%20Series%20B%20FRN%2021.3.bmp


As you can see, the OS FRN has been upgraded from 15.2 to 21.3, but the Processor FRN, or BOOT FRN, still remains at 3.0. Incidentally, the Processor hardware will remain fixed at Series B as well.

Whatever your current OS FRN for these controllers is, it could never have been OS FRN 3, if the hardware is Series B. They could only have been sold with OS FRN 11 minimum. If Series B, and so at a higher OS FRN, then the possibility of the FRN 3 issue in the technote is irrelevant now.

As a by the way, OS FRN 4 specifically addressed this issue and states as such in the firmware release notes...

ML1400 Release Notes said:
Corrected Anomalies for FRN 4 (Series A only)
Anomaly Description: 71h fault with I/O expansion modules
Under the following conditions, a 71h fault may occur within a few minutes:

1762-OF4 (Series A, Revision B/C) or 1762-IF2OF2 (Series A, Revision D/E) expansion module is used, and scantime hits less than approximately 390 ms (usually when user ladder program is empty).

If your controllers are at the likes of OS FRN 15.x or above, then this potential cause has, according to Rockwell, long since been flashed out of existence.

Geospark said:
...I would also like to rule this in or out...

It looks like your screenshots may have helped rule this cause "out", but do please confirm those details?

If ruled out, you are then back to the good installation practices you are being advised on and have started to follow.

All said and done, it never hurts to flash upgrade these controllers to the latest in an effort to remove certain anomalies...

Steve Jackson said:
I downloaded Version 11 earlier through Rockwell. I am fine with using Version 12 or whichever one will work. My RSLogix 500 is Version 9, so that would need to be considered.

My best advice - If your MicroLogix 1400 controllers are Series B, then download OS FRN 21.3 and flash them to the latest available. That is the "one" that should "work" the best.

Your RSLogix 500 software version is not directly tied, or "lock stepped", as it's known, to the controller firmware revision you are currently using. Although, there can be certain features, which are introduced in certain FRN releases, which will require a minimum version of the software to use those features. The new password features added in RSLogix 500 v11 / OS FRN 21 would be one example. However, a previous version of the software should still work with a controller flashed to the newer FRN - except the newer features, available in the controller FRN, will not be exposed to the software.

Regards,
George
 
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