Measuring regulator values on H745

Okay, I was trying to find out if my H745 is shady, so I busted out the DVM and put the probes on the blue wire and a ground wire. (blue is supposed to be -15v) Nothing. Okay, so just to check my logic, I hooked the probe to what is supposed to be a +5v line and a ground on the same connector, and the light on the 7441 regulator goes out. Nothing on the DVM. The DVM is set to "20" in the "DC volts" area (it's one of those yellow dial type DVMs) Deposits work, but exams cause a bus error. My power supply isn't shot in all areas, so how am I measuring this wrong? I'm measuring at the power control board, where the backplane connectors are plugged in, and I'm using the BA11-K manual and prints as a reference for the wire values. What am I doing wrong?