I'd bet you have a burnt cable where it wraps around the mdu.

Start with one meter lead at the battery pos (keep that one there), then check voltage to the pos. side of the armature, load it and watch for a voltage drop. Should be around 0 volts DC.
Move to the next armature motor post, try again. If you see a big voltage, then the motor brushes are to blame.
If ~0vdc, then move to then direction contacts, in particular, the bar the joins the 2 top posts.
Load it, ~0vdc= cable ok.
Then move to the bar that angles over the side of the contactor, on the side that you close with the the dir. switch.
Load it, ~0vdc= conator ok on that side.
Then follow the cable to the field post on the drive motor.
Load it, ~0vdc = cable ok.
Go to the other filed post on the motor.
Load it, ~0vdc = fields ok.
Then back to the dir. contactors, on the opposite angled buss bar.
Load it, ~ovdc = cable ok
Then to the 1 cable left on the direction contactor.
Then bottom one with the cable only.
Load it ~0vdc = contact ok.
Then move to the m- post on the pmc.
Load it, ~0vdc = cable ok

** when I say load it, try to drive the unit... close a direction contact and either trust the pmc, or short the batt neg to the m- terminal (with the wheel off the ground of course)

If you can pass all these tests & the motor doesn't drive when you close a direction contact while shorting batt neg to m-, then you screwed up somewhere and need to start again.