311: I'm out of ideas

Hey, kids. I'd be most grateful if one of you can point me in the right direction. I've been working on this for a couple weeks, and I'm out of ideas.

Symptoms from inside the car:
Running normally, come to a floor, door opens, door closes. Immediately the annunciator reports "We are experiencing technical difficulties." All car calls drop. After between 5-15 seconds, the car will once again take car calls and all is well. The elevator can go for a day, or sometimes the symptom occurs after 10-20 runs.

The problem occurs in both up and down directions. It also occurs after I've taken the car out of the group and turned off door operation.

Symptoms from the machine room:
Everything is running normally, and then all of a sudden in will go to NAV. After a few seconds, it will go back to NOR. The MCSS faults show a 2700 and a 2702. However, the brake is not the cause, but that's the first thing the computer picks up. Those are the ONLY two faults, and they occur EVERY time this event happens. What I DON'T get is a U or a D. They turn on through the MCB board, but I don't know what happens prior to that, to turn on the XU and XD signals. I can see that they're turned on by modules on the board, but that's it.

What I've tried:
I've replaced the MCB with one from Otis. I've replaced all the relays that turn on with the self check (CIO?). And today I replaced the Ring Board.

Any ideas what direction I can take this on Monday morning? I can go 150 runs with everything ok, and then all of a sudden I'll fail to get the XU or XD from the MCB. I'm stumped.

Thanks.

Rusty
You say "it's not the brake", although both your faults point to it. I don't know what faults 2700 and 2702 are exactly (obviously brake related), but let me ask, is there a brake switch on the brake itself? If so, have you metered the contacts opened and closed? Sluggish to drop the switch contact after a run can generate faults.
Or if no switch is present, have you checked the brake relay itself?

Bad or intermittent micro switches on the brake. replace them.

Thanks, folks. The brake was the first thing addressed after seeing 2700's and 2702's. But on a 311, the brake isn't supposed to pick until the MCB turns on XU or XD. That's what's not happening.

The fault is saying that its not seeing the expected brake state from the sounds of it and yes the micro switches notoriously go bad ( I have had to change pretty much all mine at least once ) but as original poster says this sounds more like a symptom than the cause . Does it show any drive faults ?

I'm uncertain, Pieman. I will look at it from that perspective on Monday.

Try turning the brake sw parameter off.

Interesting idea, FA.
I don't know how to do that.
Do you have a procedure or address?

If nothing else, if the car doesn't shut down for the brake fault, it might give me more time to watch and see what's happening.

Thx.

Brake switch monitoring is in the drive parameters, I believe it will say 'brake switch present? ' and the options are 0 and 1 . If you say there are no brake switches you have to jump them out in the controller also. I'm on a gen 2 in the morning, I will post the exact sequence she I have a service tool in my hand.

Thanks! I was looking at the MCSS and OCSS, and didn't even think of turning off the monitoring through the drive. I'll try to cruise by tomorrow and give this a try.

Its in the brake / dbr parameters in the drive set up ,module 4_3_1_3
Brk sw pres
Change to 0
Jump out brake switches in controller .
You should only do this as long as it takes to prove the switches are or are not the fault tho . If they are then Otis sell a replacement kit .

Thanks, Pie.
The problem might be resolved. Once again, this morning I went over all the basic things and found nothing of consequence. So I set up to watch the drive's LVIB (specifically the U30, UDX, and the UDX LED).

200 runs later, there were no anomalies, so I turned the car loose. It's at 306 uneventful runs as I type this.

I didn't disable brake monitoring, as I didn't figure out the secret key codes until just now.

Gonna watch it some more.

You gotta hate jobs like that . if you open up the swing panel with MLB on it you will see two LED's B and BE on the terminal rack , these indicate the brake switch state . if your lucky enough to be watching those when the fault occurs then that may give it away . you can also have issues with the drive LVIB itself . in my experience if its the brake switches it will return and get progressively worse . if you do need to change them they are a easy swap out , 7 mm wrench and long nosed pliers make it easier . I had a fault on a unit several months ago that I could watch for hours on end and the minute I left would happen again , trapping people but showing no fault by time I arrived. I spent 7 straight hours sat watching the controller putting in random calls , had lunch and a Thermos of coffee in the machine room , after 7 hours I needed the bathroom and couldn't hang on any longer , the bathroom was just far enough away that I could hear the alarm bell ringing just as I was washing my hands . had corrected by the time I got back to machine room . one of those days you wish you took another career path

:-)
Nah, I dig a challenge... as long as I don't let the pressure get to me. That is the REAL challenge. This one went on too long. Hopefully tomorrow's new challenge will be easier.