
On the C6 it's on the drivers side of the radiator sitting on top of the main chassis rail, essentially to the right of the suspension pump looking from the front. It'll be a fairly large, probably brown, relay. you need to confirm there's 12v on one of the two thicker wires. If there is, pull the relay, make up a jump lead from wire of a suitable size and bridge the two thick wires. That should put 12v straight to the motor connector. There should also be 12v on a smaller (trigger) wire for the relay coil. If this is absent go check F13 on the BSI. Also if you haven't already done so, remove and reseat MF4 (the big one under the engine bay fuse box (BSM)) they have been known to go high resistance and, although they measure continuity okay with a meter, they don't pass the level of current required to run a motor.
Marc,
do you have a copy of the diagram that lists the component No.'s and their locations (part of the loom layout I think)? That'll help me direct Jay to the correct locations.
Cheers