Find which wires are what in a sjt power cable
There's something very ugly with your electrical wiring. The center pin of the block connector which goes into the computer has to be the earth/ground wire - no exceptions. 

You should measure a low voltage between the center line and one side (less than 10V probably) and nearly 115V to the other side (='line').

In you case A-B + B-C = A-C, which is fine, but the you really should not have such large voltages on both sides of ground.