blue/white wire from alternator

[Tattooman]

which route does this wire take from engine into the cabin? on the drivers side there is a wiring loom that goes through a large grommet into the cab. i split the plastic surround to peep inside and amongst a load of other wires is a blue/white wire. would this be the one from the alternator, or is there another blue/white wire? don't suppose the alternator wire goes anywhere behind the cabin fuse box to be accessed from there does it?also been told the wiring loom containing the wire enters the car near the brake servo, thus can it be accessed from behind the glovebox? don't want to have to take the dash apart to get at it behind the instrument cluster.need to access it to wire my split charge relay. are there any other wires i can tap into, wires that are live when the engine is running, but not live when cranking?