it sounds like the slowdown and braking with empty car being the hardest to pull up. i would be going over all slow down ccts, brushes and contacts on the selector( particular attn to the advancer stop contact at the top of the selector). i would constantly run the lift into the top floor before this to try to get the fault to appear(and maybe tie the safety gear up so you dont have to release it) but most likely its too intermittant for it to appear. it could also be rolling up from the top landing which is something to look at also. you might be able to slow the lift top speed to mask it if you cant find the fault. in these situations ive also wired in test relays to see what certain relay states were present when the fault has occured. you would like to know wether the sls switches have worked so i would fit slave relays to the speeds ie 1e,2e,3e etc. you wire them the reset when the lift takes off again but if it goes thru the overtravel these relays will stay on to indicate wether the speeds dropped out.

Work Safe,

Jim

There is one thing that I have noticed, the elevator starts out on highs speed(1a), when it comes to the designated floor there is a 1 and 1/2 second delay between the dropping out of 1a and the picking up of 2a, there is not a delay between 2a and 3a. The elevator is in momentum mode during this delay.

Car b has the same delay and it has not ran into the overhead.

We made a couple of adjustments to the resistors on X2a and X3a on Car a to duplicate what Car b is doing.

Other than those two items, the cars appear to be doing the same thing.

Jim, it is not breaking traction. That was the first item we checked when the problem started. However,anything is possible.

If the car is braking properly and not slipping traction then you have a control problem. Place the car on inspection and run it on and off the floor limit. Then bypass the floor limit and run the car from the car top inspection to observe the terminal landing limit and final. Make sure they are all opening and closing properly.

Last turn the power off and check the relays. See if any contacts that should be open are! Look and see if the contacts on each relay open and close at the same time. A bent contact could hinder the way a relay operates.

first thing id do is place a piece of paper across t,g,u to test wether you have a residual magnetism fault(night call trick). also make sure the mechanical interlocks is not busted either. also check your brake adjustment and the brake drum is clean. also if you have to reset the safety gear as well then the lift is just not slowing down as most of the time it will just trip the overtravel limit. also check the eveness of the brushes on the drive relays as they can cause irregularities of current flow to the ac machine. i would also check the sd relay function action as if it is slow or sticking it will effect what position in the shaft the lift starts to stop which for that level and load is critical. also check the leads on the contacts as they might be braking internally.

try these out and let me know.

Which 6850 model are you working on?
Model CA, CK, or BV?
What is the car speed?
Which controller 10, 11, 12N, 21, 23U, 30N, 30u, 30UAL, 30UCL?
How many contacts on the contact bar 12 or 19?
Is the ring lifting all the way up?
Is the ring dropping down properly?
Are LV2 or LV6 bouncing, burnt or the brush tip worn?
Check for worn, pitted or missing floor bar brushes?