Here are more details of what I've found. Connecting between C29 and A12, A13 the brake coils test about 30 ohms each so they are ok. Diodes D2 and D3 test well too, holding in one direction and showing half a volt in the other using my checker.
Stored codes show 226 six times, each with a 209 code too, some left, some right. The first 226 was 122 traction hours ago. There are no 52L or 52R codes stored.

Three traction hours ago there was a 240 code - slave detects problem in master?

The controller may have a problem in the brake driver. I've taken the cover off - quite pristine inside - all looks new, no burn smells. The original seller has offered to send it out for diagnosis.

Motor encoders are in the end bearing inside the drive motors. There is a connector located on the brake end of the motor. The wires run into the motor. You can run resistance tests across the pins and compare one encoder to the other. Usually it is the encoder on the side that is throwing codes.

compressed air (if you have a fine bristle brush that will fit in those small spaces that might work ok too)
do not use water period! no degreaser either

you can use motor cleaner or contact cleaner
anything that will evaporate quickly and is designed for cleaning electrical components or motors.
Just make sure you unplug the battery and discharge any capacitors on the panel if any. Alot of times pressing the horn will discharge any residual power stored in any circuits.

question - is there a preferred method for cleaning the inside? It's covered in years of dirt. Compressed air and a small brush in the controls compartment ?
can the hydraulic pump area stand water? degreaser?

And thanks, swoop223. Good comments about how a bad coil could still release the parking brake. The driver needs to connect both ends of the coil. I'm gaining on documentation - found a copy of the AC controller manual. Don't know if I'll get this truck going, but at least I'll know more than I did!

Thanks Brewski - I'm new to this - where is the motor encoder? Can it be checked without ETACC? do you know which ETACC rev includes model F807?

Do check the motor encoder. We had one throw the same codes and it was the encoder. We have also seen the controller be the problem.

the jumper in the harness in the right wheel well is actually the jumper to allow for towing, it will manually release the brakes so you can move/tow the truck.
As for the error that is generated by the controller, it is still faulting out because it still sees an issue with the park brake circuit even if the harness is bypassed for towing.
Your seeing the 209L because the controller is seeing the park brake still applied because of the fault from the brake driver triggering the 226 code.

Now as for the 209L code troubleshooting says to check the following:
* Electric brake will not release.
Recycle key switch.
* Check for voltage at the brake coil.
Should read approximately 36 volts.
* If no voltage, check wiring for loose connection or
broken wire.
* Check motor encoder. See Status Code 52.
* Check brake circuit diodes.

I think you'll find your not getting the negative at the brake coil from the controller signal and since you did the bypass with the tow jumper you know the coil is working. So you need to back trace and check the wiring and connections (and diode on wire 50G).

As for the fault 226, brake coil driver, here are the checks for it:
* Disconnect connector C from controller.
Check for short between B and C28.
The brake coil resistance is approximately 31
ohms.
(if this test fails you have a bad controller and it needs to be replaced as the brake coil driver is internal inside the controller.

Good luck

Some history - truck was functioning ok - but cutting out (stopping) occasionally - moving around in the seat usually got it going again. One day it just stopped - parking brakes locked on. It was towed a few feet out of the way and has not been used since. Fuses I can find are ok.

Yesterday with battery charged up, I released the parking brakes by swapping the plug-in for towing (by the right front wheel). With the power switch pulled ON, the brake release sound was heard and the machine became free to roll. That's good news (I think). But the error code 209L says the brake coil is open or shorted. How can a bad coil still release the brakes? The other code is 226 - which is the "brake driver". Is that a separate module somewhere? Anyone here have experience with ETACC diagnostics? Does it help in diagnosing the machine cutting out? The S/N is F807N05799F.

yes
the display will probably show 0.00
if you pay attention to the display it will start out with something like dashes ----- , once connected it will react when you connect the leads, showing there is continuity, if there is no reaction on the display and it does not go to infinity (0.00) then the fuse is open. Or if it does not reach infinity and shows anything higher than 0.00 there is resistance that should not be there indicating the fuse might be partially blown.

" locate any fuses you can find and check them with a vom....... i would suggest removing them from their sockets first and check them with the vom in ohm or resistance scale, they should read infinity [???] on the meter any open or excessive resistance indicates a potential issue and the fuse should be replaced."

Good fuses should measure ZERO ohms, right?

Thanks for the reply - I'll do some checking.

you can attempt to purchase a service book from your yale dealer, there is no guarantee they will sell it to you though. They might , then again they might not.
Based on your description and comments and the fact you are new to lift truck repair i'll say this:
- based on the model of this truck even with a service book you will be challenged to attempt to repair this truck
-other than checking fuses and battery you would most likely need the pc program to aid in further diagnostics

so based on the codes being displayed i would do this
a) check the battery charge, if it is a flooded cell battery make sure the water level is above the cell plates and make sure it is charged up.
a low battery can cause these codes. If the battery is charged and no other issues are found then there may be some other problem with the bdi circuit and/or configuration in the vcm.
b) remove the control panel cover which should be located underneath the seat/hood and gain access to the components on the panel and locate any fuses you can find and check them with a vom, The may be fuses located underneath the floor plates or on/in the steering column as well, i would suggest removing them from their sockets first and check them with the vom in ohm or resistance scale, they should read infinity on the meter, any open or excessive resistance indicates a potential issue and the fuse should be replaced.

Beyond this i would call a dealer to send out a tech

you can attempt to purchase a manual from your yale dealer, there is no guarantee they will sell it to you though. They might , then again they might not.
Based on your description and comments and the fact you are new to lift truck repair i'll say this:
- based on the model of this truck even with a manual you will be challenged to attempt to repair this truck
-other than checking fuses and battery you would most likely need the pc program to aid in further diagnostics

so based on the codes being displayed i would do this
a) check the battery charge, if it is a flooded cell battery make sure the water level is above the cell plates and make sure it is charged up.
a low battery can cause these codes. If the battery is charged and no other issues are found then there may be some other problem with the bdi circuit and/or configuration in the vcm.
b) remove the control panel cover which should be located underneath the seat/hood and gain access to the components on the panel and locate any fuses you can find and check them with a vom, The may be fuses located underneath the floor plates or on/in the steering column as well, i would suggest removing them from their sockets first and check them with the vom in ohm or resistance scale, they should read infinity on the meter, any open or excessive resistance indicates a potential issue and the fuse should be replaced.

Beyond this i would call a dealer to send out a tech

Contact your local Yale dealer. They will sell you a manual.

Thanks for the quick reply.

Is there manual I can order to explain how to work on this rig?

I'm helping a fellow apple grower deal with his Yale. I've worked on tractors but not electric lift trucks. Harvest is upon us and I'd like to get this working. There's no motion or lift when turning on the key.