The interesting thing is that the voltage spike on B- to chassis only happens when the PSDM switch in the ON position!
Interesting.
Try disconnecting your charger Red cable and see if it is still there.
Q-> When you installed this charger, There are 4 wires on the output. Red, Black, White and Green.
What did you do with the Green wire?
Still there with red cable disconnected.
Green wire connected to another green wire.
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K. You can see if the jump is coming from the controller.
Disconnect the POS cable and try again.
Is there anything connected to A or B on the front of the controller?
Don’t see anything unusual coming from controller.
Disconnected the POS from PSDM and no voltage B- to frame.
Nothing connected to A or B.
Happy Holidays to all and Merry Christmas
Apologies, those were horrible instructions.
Interesting development tho. (let’s follow that)
Reconnect B+(+72V) cable to the front side (driver) of the PSDM and verify that measuring B- and Frame that phanom B+ has returned. What V do you actually get?
PSDM
(One at a time) Unplug all of the harness connectors(J1 to J6) going around the perimeter of the PSDM, checking for your phantom V to disappear.
Return with your results.
When I connect the red lead from voltmeter to B- and black lead to frame -76v.
The first one I unplugged was J5 and Voltage gone. I did do all the rest J plugs and only J5 made the difference.
At the controller is where I had the sparks fly when hit with wrench the frame with hot B+ on frame.
Yep. That is understood now. The evidence at the rear cable was odd until you mentioned the sparks up front.
J5 and Voltage gone
Interesting. J5 is controller harness. Let me see if I can track down the next move.
88 posts from a bunch of guys complaing about something getting blown.
Whoda thunk it?
I’m surprised it took 88 for that little light to go on.
Sorry, i was preoccupied
Life is like a box of chocolates!
Surprised? Didn’t you see the ruckus Monica Lewinski caused? 
Heard it was hands off. You’re not the least bit curious?
Happy New Year. Any thoughts?
Ah, Right.
Sorry, you were drowned out by the holiday rush. Back at it.
What motor are you running in this car? Is it using the temp sensor wire that runs down to the motor? There are two sensors running down to the outboard end. A 3 wire group is the Speed sensor. and a 2 wire being the temp sensor. Unplug the 2 wire connector (if still plugged in) and measure for the stray Voltage.
More likely is the Motor Controller. It has the large 23pin connector on top. Unplug that and check for the stray Voltage.
Report back with results.
When unplugged the 2 wires from the motor the voltage dropped 2v more or less. Then plugged in again.
When unplugged the 23pin harness the voltage remained around 70v.
Pretty crazy. There is not too much left on J5 that could be leaking B+ to Chass.
There are 6 nuts on studs holding the controller down to the chass. Remove them and lift the controller up just high enough to slip some cardboard in between it and the chass so it doesn’t fall back down on the studs.
Leave all wires still connected and check again.
Results?
Still reading 78v when lifting controller off chassis.