Hi if it don't run in conventional check the current draw if it still is
amps on transformer at .01, at 18 volts,
with SD35 on track, amps at .02.
then I would suspect you're board is blown, you can get an ASC MTH TECH to test it for you , where do you live I'm in NJ
As Vernon said if it is a 2/3 engine the switch can be bad or there could be corrosion on the pickup or even with poor grounds on the trucks ,ps3/2 were the worst design all these engine have had issues ! they are all repairable !
Alan