ok so what i'm to understand is this is a reman/rebuilt controller from FSIP? Not an OEM replacement from NACCO? correct?

ok... LTRM does have a point
i'm sure the guy has checked the main fuse and its not blown?

if all the above is good maybe they should try and get gesentry and a cable and try to access the unit using a laptop when powered on and see if they can even communicate with it.. that should tell the story. I do know for a fact that FSIP does not restore manufacturer specific settings in these and it is possible that the settings may be set to GE defaults, so there could be a setting incorrect. But then again it should code out when powered on. The fact that it is kicking the line contactor out when it tries to turn the system on fully initialized still makes me wonder if there is a hardware/hardwired fault.

If access cannot be achieved via laptop then the rebuilt controller is probably no good. Before anyone says anything about Yale software access through the dash, i am aware of this but you can still access it directly through the port on the controller if you have the right cable using gesentry.
At least to my last recollection this could be done unless they have made some drastic changes in thier dash access system and changed this method of communication through the onboard logics. But the SX controller hasn't changed much on GE's part as far as i know so it should work.

the controller is the exact same part number...from a reliable source..FSIP. no adjustments were made to settings prior to install. i will pass along your info to my tech. i will get back with more details. thanks..

The number one cause of code 66 is a blown drive fuse. I have been burned. The book does not mention it.

"cross the terminals on A1 and A2 it may have some strange effect"
that "effect" is running the wrong direction.

where did this 'other' controller come from?
is it new? or just swapped out from another truck?
is it the same type/model controller?

there is a slight possibility that it could be wired up wrong but the cables are pretty much in thier respective places and it would be hard to get the armature and field cables mixed up. If he happened to cross the terminals on A1 and A2 it may have some strange effect such as this. Also could be the wrong controller.

edwardt is on track tho with the info he posted. Maybe you should backtrack and make sure before you blow another controller. :o)

As for a setting causing this? That would only happen after the truck starts up and it would code out, not what you are describing. Now there could be some setting that might cause this but generally it would code out as i already said.
The controller goes into a 'self check' when turned on and it is seeing a problem when the line contactor pulls in and is shutting the controller back off to help protect it. Most likely a wiring or motor issue.

I've often seen code 66 being related to a missing suppression on the horn or the wrong horn being fitted with suppression missing.

1st, is the battery well charged? and does it have any sort of 'short to frame' that has less than 100k ohms?
2nd did you set up the controller with a handset or computer so the settings match the truck's specs?
3rd are you SURE this is the proper controller (part number), and not a 'looks and fits the same" controller.
Code 66, on a GE SX traction controller indicates (to me anyway) either a problem with the drive motor, power cables or the traction contactors, and would extremely rarely be the controller itself. if someone has changed the contactor assembly, it may be that the coils in the new assembly were not the proper type.
The book says a code 66 is "The field current exceeds the current
limit of the field transistor".
POSSIBLE CAUSES
Shorted field F1 to F2 *=F1 or F2 terminals shorted to battery positive (B+) or to battery negative (B-)
Binding line contactor *=Visually inspect tips, clean them with a
solvent. *=Confirm that contactor includes G248 coil.
Noise *=Missing or damaged horn suppressor
Confirm that all inductive loads/accessories are suppressed.

I know I have seen code 66 from power cables being routed too close to the control circuits, but that was intermittent and related to the traction load (up ramp set the code from EMF noise)

you did put the big cables for the armature and the little cables for the field?