Could also be the tach or encoder. Had a bugger of a T4 problem awhile back and that turned out to be the drive (DC). That one would also stop in flight along with many other issues.

Which faults?
Directional?

Not a lot of info with your post.

mostly 56 and 54 errors occasional 55 -from the info I have it leads you in numerous directions from bad board to inputs etc -well the relays are on order if that doesnt fix the prob - guess it becomes a elimination game -not to fond of the t4 lol

A 55 fault is usually caused by clipping door locks. Check the locks and gate.

already checked the locks --even found some bad pick up rollers lol getting the maintenance done shooting some trouble

the 55 flt probably was me picking the lock in flight --my gear is on the job and I remember the 55 flt but this is my first t4 so i'm not familiar with remembering what all flt numbes are -disregaurd the 55

Is it in one direction?

Connections, connections, connections on T4, also aux. contacts, brake and M contactor contacts.

I struggled with one that wound up being the voltage monitor. After the unit ran a while it heated up, started drawing more across a weak voltage monitor and it would fault quickly and reset causing a cycle affect on everything and throwing many non related faults from the CPU.

I agree with Engine31, check the voltage of you power supplies also...

What drive do you have, DSD 412?????

thanks for the geat ideas and comments -grasping for straws on this one but this is a job that is not mine im just temping out of town on a another brothers route -I will check the drive info and get back on here for a update -I was tipped in leading towards the aux contacts and relays on the unit -only monday will tell but I greatly appreciate every suggestion that everyone has -this is a great forum that I just happened to find -thanks again brothers have a great weekend and always work safely

it seems to happen as the car takes off - acts as if it is clipping locks- but its not clipping locks have ran the the hoistway and checked them already-- it will do it at various floors and only in the up direction leaving the floor -

How about that pit equipment? Gov tension sheave etc.

robert I believe this unit does not have the tail sheave switch feature -its a walk in pit so Ill take a gander but wouldnt a flt or error code show up in the safety string or something of that nature -me being unfamiliar with this unit im not sure -but I will look into it -thanks for the lead

you may have some "tired" modules in your card rack also, being its a T4 which I suspect may be 15-20 years old. also, clean and reseat the cards.

try running it on machine room inspection and wiggle the card rack, see if it shuts down.

send me a plane ticket, id be more than happy to find the problem... LOL !!! 2 hours tops when I get on site. ( at 1 time i was a regional adjuster for TKE, back home with the big O now, 33 years in business )