I wasn't present for the troubleshooting, but a request was made to help change the Electrical Power Management Panel for erroneous A/C-D/C voltage indications.
The cockpit overhead panel needs to dropped down. On GIV's, both of the L/H-R/H overhead circuit breakers panel covers need to come off.
One pain-in-the-ass aspect of an EPMP change is the fact that the inboard panel mounting screws (3 ea) are covered by the adjacent fuel system light-plate. That plate must come off which would seem simple, but...... the two guarded switches (APU Fire Bottle and Fuel Intertank) have to slide out with the light-plate as the plate itself will not clear the plastic/metal of the guard.
The center and left aft cockpit headliner panels need to be removed of pushed aside to gain-access-to (my favorite words in aviation) the panel disconnect plugs (4ea, 2 left, 2 right) mounted on the frame rib. Gulfstream didn't exactly provide a ton of room between the plugs, so using any type of cannon plug pliers for plug removal is impossible.
The odd numbered plugs (1 and 3) are mounted aircraft left.
The even numbered plugs, aircraft right. And yes....... the add-on black plug and relay "do" get in the way.