My thought was that the problem could possibly lie in that switch. (?) However, 1000 amps from an SW8 in Run-1 exceeds what the engine should produce if running light. If coupled to cars and the 2-position excitation switch is defective and making the locomotive load fast regardless of switch position, then perhaps 1000 amps could be developed intentionally if the unit has not initiated movement.
Your concern, though, as I understand it, is not the amount of amperage, but rather the speed at which it is obtained. If you can test to see if the 2-position excitation switch output does not change on its own when your high excitation occurs, at least you would know for sure whether it is the culprit.
