I had a similar problem, it turned out to be the valve wasn't sized correctly. When the car went to heat the oil it would push up the hoistway till low oil kicked in. We would find the car on the Buffers with weird faults. Just something to look at.

ill check it out thanks john

Might be a good idea to also check your power supply voltage at EPROMS on Main Board. Make sure you have 5.2vdc with very low ripple on top right (+) and bottom left (-) pins of a chip. If voltage is set at PS, (.5) volt can be lost in wiring. Ripple can be checked by putting a True RMS meter on AC and checking the 5.2 volts. AC should read close to zero.

Wouldn't hurt to clean the reflector and change the switches since you already changed the FCB/HVM. Checking bypass is also a good idea.

i cant remember the times but if MPH 2 relevel 3 or 4 time in less than "xx" time without move from this floor, the computer move out of service
you must check beam sw clean and adjust if need , but if you found the cab down level in the PIT you have a VALVE problem or a broken vitaulic

You would get a "re-level prob" for that one.

eman, you are correct, i have seen the relevel message a few times, and have been able to resolve by replacing both lu and ld sensors. just never saw this error message before. i will check all the above advice. thanks again.

An mph,if the top slow down is less than zero resistance will decide it cannot leave the bottom floor. It will step out,run a few inches, advance to top, return to one, and report an optic failure. Reset and it will run a few days.

ended up changing both lu an ld switches, and it has been running for a couple weeks now. time will tell, thanks for the input haughtoneer, i was trying to duplicate the error message, and i did remove the top slowdown wire from controller, and try to run the car, it would not get the same error message . the error message was photoswitch error, shorted ld. the mechanic said it just said shorted ld, or shorted lu. when i saw the actual error it had the photoswitch error, shorted ld, that is when i changed both sensors, and all has been good so far.

The way I understand it, kind of like an Optical Leveling Failure on a Composite. If any two switches change state at a time that's physically impossible, it fires the photo eye short. Aside from having false fires from foreign reflective spots in the hatch, replacing the PCB and LZD's usually takes care of those issues. Glad it's running.

I was going to say something similar to john jay. My issue was the valve adjustment nut came loose and allowed the valve port to come out of adjustment, that caused the elevator to run up slow when the car was warming the oil by running the motor and pump(cold oil mode)