(T) wiring fault AAAAH!

Hi all, got a strange prob with radio wiring only.
got a Black (earth), Red/Green (continuous live) & a Pink (also continuous live) from my SX into a ford standard radio. When I put tester between negative post & lead on battery, it lights up UNTIL I unplug radio. Tried radio direct from battery no drain ?
My manual does not mention the pink wire at all?
It appears I have a leak in the negative side of the cars wiring but only to the radio circuitry, the wiring traces back from radio to a plug under the heater vent above left dash speaker?
Wired direct to posts on battery = no leak, wired from + post & -lead to radio also leaks? Done my head in all week. Thanx 4 any help/advice.

regards.....cj

Sounds like the pink wire is connected into another circuit, not just a switched positive.

Pete.
Cinq sporting 1242cc
Cinqs&Seis Yahoo group
Clubcento

Thanx Pete, kind of given up on it for now, the radio harness joins another main harness wrapped in grey foam, under the dash just to the left of the centre console, and this goes into way too many relays and boxes for me ! Checked every wiring diagram in my haynes manual & that pink wire definately should not be where it is lol.
Perhaps a previous owner had something added which was later removed,just got to try a different brand of radio as a last elimination process, with only 1 positive connector, as I've tried 3 types of ford & they all need the live feed to pin 1 & 3.

regards.....cj

perhaps the pink wire is the switched live for the fiat radio and the ford unit is feeding some circuits through it, try cutting it?