Otis 211 Hydro

Having an issue with this unit. Keeps going down every other day. So far has gone down 3 times since 11/25/20. Faults have been ULFB. SHD.
DMFB. SHD.
UMFB SHD.
All of them reset easily and it runs after. Any ideas what I should be looking to or for for the possible issue here? My first impression is these are valve coil/valve related issues. But I have taken apart and cleaned the screens and stem seats. No change in observable operation. Any thoughts anyone?

Anyone?

It means the valve output was turned on but the feedback input didn’t see the voltage or the feedback input saw a voltage when the valve output was not turned on. For it to happen with 3 of the 4 valves is weird. Only thing in common with all the valves is the safety string. Maybe a flakey contact in there somewhere or a loose connection.

Maddening... Where do I look to fix this then? Replace valve coils? Replace selector board for possibly sending erroneous signals?

Is the car sinking, releveling?

Not routinely. It did do a dance when the oil was cold one time, settled and releveled and shot through and leveled down. Only saw that once with cold oil and it didn't shut it down.

Make sure to isolate hydraulic leaks, via doing a sit test. I don’t know but maybe its going down mechanically and causing the lift to fault out.

According to a 418 page manual I read there are 2 possibilities for this fault. 1. Directional limit tripped while the valve coil is picked/energized. 2. Mother board component u78 is bad and generating false signal.. So we have gone through all the HW switches and adjusted the UP final further away from the landing by 1/2" incase the unit it intermittently leveling through or shooting through the floor.. We will see how it goes.

The problem with that is you have had both up and down valve faults so 1 directional limit switch can’t account for all of your faults. I suspect the board.

Yeah... That was my concern too. But to rule it out we adjusted it any way. But it's down again today. So not sure how we are gonna proceed now..

The valve seems pretty solid. Not releveling a lot. But these faults all say Valve feedback.. Scratching my head on this one..

I guess we will try replacing the selector board and rule that out. Possible false signals being generated by the selector..

Replaced selector board. And it was down again today. So today we replaced the stems/seats on the maxton valve to rule out that section of the valve at least... We will see tomorrow.

It appears that replacing the stems and seats on the maxton valve has repaired the issue. Original issue being a SHD status with one of the following faults. ULFB UMFB DMFB DLFB.

Well it worked for a few days. Now its putting up a RECF. Any one else have any ideas?

Is RECF a “recycle” fault? Otis’ version of viscosity control?

That would help explain the other Valve related faults... Our next step is replacing the valve. Will see how that goes.

Sounds like your bypass isn’t set right and car is moving when it goes into “recycle” mode.