Thanks for "swooping"...
The arcing is mostly cured. It was possible to replace brushes & springs without removing the motor. It lays below the floor - taking out one bolt and loosening another allows it to rotate up for access. Brushes were worn, some were hanging up. Springs were rusted. A general cleanup and new parts has restored good running. Ordered a stone to clean up the commutator.

you should be able to clean or change the brushes with the motor in place.
use electric motor cleaner and blow out with compressed air to dry out any residual moisture.
If you change brushes make sure the sensor wires (if any) are not rubbing any other components. Make sure the springs seat well.
After installing the brushes it is a best practice to use a brush seating stone to clean the armature and help seat the brushes to avoid any excess arcing. New brushes do not form to the armature as one might think so you should use a seating stone on the armature to clean the armature and help the brushes seat properly.
This may take 2 people to perform this, one to operate the pump circuit and the other to use the stone on the armature while the motor is running.
Do not get too carried away with cleaning and seating, it only takes a small amount of pressure and watching the armature, once it looks clean and the arc'ing is minimal is when you know your done.
There will always be a small amount of arc'ing due to the nature of the contact surface, you just don't want to see an excess amount of it.

You can get these seating stones from any motor servicing business or from the dealer.

So after about a month of good performance, the hydraulic levers cause the contactor to click but no lift, tilt, or sideshift. Operator reported lift was SLOWING down and making noise as it went. Then stopped.

Took up the floor covers and nudged the pump motor fan with a plastic pointer - motor starts but arcs (that's the noise heard when it slowed). Pretty sure its brushes hanging up.

Looks like they can maybe be changed with motor in place? Any guidance very welcome. Thanks.

well they can be if you don't keep the battery charged up good but all in all the tips will burn over time, you just have to check them occasionally.
Generally if you start seeing pits in them or material transfering from one side and see it stuck on the other side thats a sign.
They will normally burn just from use so don't be alarmed if you see that, just as long as it's even across the tip surface.

As for a transistor option that does eliminate the contactor issue but you have to deal with the lever switches or sensors that can give problems.
Also the transistor controller is just as expensive as the drive controller, probably about $2500, a reman one probably around $1800, but that all depends on which one it has, prices vary somewhat.
If your using the truck a lot it may be worth the upgrade but if not then i'd just stick with the contact tips, they are a lot cheaper to replace :o) a tip kit is about $100. You may can find them cheaper in aftermarket.
If your use is not heavy and you just put a few hours on it a week chances are you won't have to replace them again for a long while.

Well today there was another glitch. Hydraulic lift stopped working (no codes). Could hear the contactor clicking so took it apart found the points looking a bit toasted. I shined them up and its working ok now. Are contactor problems common with these? I see Yale offered a transistor option - maybe less maintenance.

good deal man
glad i could be of some help

The battery came back from the shop today - looks brand new and a full charge fills most of the bar graph on the dash - best it's been in 3 years. First attempt to move briefly showed a 209. Sprayed the controller plug-ins with contact cleaner and re-seated them. Brakes released and truck is now working fine with no codes.

I recalibrated the accelerator and steering - this time voltages displayed on the dash were normal. Thanks again for your help. The Yale is back in service just in time.

If your checking the accelerator with a digital vom it will appear to be jumpy, the best vom to check the sweep with is an analog meter.
If it is still erratic and not passing calibration then it will have to be replaced.

The present plan is to service the existing battery and put it back in - no new cells.

Thanks to you guys I've been getting an education here - I had no experience with electric lift trucks or batteries. Back when I grew apples, a bigger grower would send his harvest crew and pick my place clean in 2 days. I'd help prepare the fleet of handling equipment beforehand.

This three-wheel Yale works well stacking full bins 7 high in controlled atmosphere storage rooms - but people like the two propane trucks too - especially if the electric is stopped with codes. If a refreshed controller and battery make the Yale reliable again maybe a more serious battery upgrade will be justifiable next time.

The reman controller instructions say to calibrate steering and accelerator pedal. Steering went ok but accelerator voltage seems erratic as pedal moves. No codes. Any thoughts?

Thanks a lot for your help and knowledge - I'll report how this turns out.

"Battery shop says cells all check ok, no stand-out bad cells - uniform voltage cell-to-cell. Sulfated from lack of use - but not as bad as they often see. It has flat plates - easier to de-sulfate?"

technically they may check ok as far as voltage stability and equal range across cells which is a good thing. The part that is not accurate is about what they said about 'sulfated from lack of use'. That's not when the main creation of sulfation occurs, sulfation is mainly created during the charge/discharge process. And one other thing is when water is added to cells over time it's the type of water used, using regular tap water is the worst because it is full of minerals which is what is the main contributor of sulfation. This is why they tell you to use 'distilled water', this water is processed and most of the minerals are filtered out which helps reduce the sulfation effect.
So they are not telling you the whole story and are just telling you the minimal reason about sulfation in the cells.
Most of the sulfation is in the bottom of the cell because it breaks loose from the cell plate and settles to the bottom of the cell.
Now as far as straight plates, that is good if they are not wavy, heat can cause the plates to warp and if that happens the cell is damaged and cannot be guaranteed to be stable or last any length of time. So straight plates is a good sign. And no, it would have no profound effect on being easier or not to de-sulfate. Also a de-sulfating charge only breaks away the sulfates from the plates and that settles on the bottom of the cell. And the effect will like brewski says will depend on how sulfated the plates are. If they say they are not as bad then the cell may be good for a while longer but like i've said its not what you can see, its the part you cant see (in the bottom).
Remember, every cell plate is designed for a predetermined number of cycles, anything you get beyond that is just a blessing but you are operating on borrowed time.
I would make them explain how the 'reconditioned warranty' they offer works (if they offer one) and how long it is for. Chances are they will only warranty the new cells they install (if any were installed), they probably won't warranty any of the old cells.

Depends on how badly it is sulfated.

Battery shop says cells all check ok, no stand-out bad cells - uniform voltage cell-to-cell. Sulfated from lack of use - but not as bad as they often see. It has flat plates - easier to de-sulfate?

a recon battery will get you by for a bit but is in no way to be considered anything close to a new battery. They check cells, replace any that are considered unsatisfactory but in the end you have a used battery and it's a 50/50 chance it will last any decent amount of time before the other cells start giving trouble. The recon warranty usually isn't very long either. It's one of those pay me now or pay me later kinda things.
Up to you (or your customer) how to proceed.

With no shorts found the controller was wired up. Key-on is now clean - no blinking dash, no codes. Lift functions & mast hydraulics are normal. Truck also moves forward & back (briefly).

The battery definitely needs attention. After key start, moving forward or back the parking brakes come on right away. I'm thinking the traction current draw overwhelms the battery. Cycling the key resets a clean start.

The battery condition barely reaches the green range after charging overnight. A brief amount of running lowers it to the red/yellow area of the display.

Is a recon battery a good way to go? Thanks for any ideas - and for reading this far.

Controller was sent to FSIP for diagnosis. - they sent back a reman controller (but no diagnosis).

There's a caution about installing the reman controller - need to check for shorts in the pump motor circuit. Not sure what I'm looking for - short to truck frame? Low resistance between motor leads? Thanks for any words of wisdom. Controller is mounted in machine but not connected - hoping to test soon.