tachometer on a Rover 111SI??

Hi all

I have a rover 100 (111si) and i have install a new dash board on the car. the old one did not have a tachometer (rev counter) but the new one does (new one is out of a rover 114 GTa) i swapped it like for like, but the tachometer does not work :( i know i need a lead for the coil (not sure if it is there or not, but i need to know where it goes as the tachometer is build on the the dash. I have 2 connecter plug one white (left head side) and one is blue (right hand side)

Anyone have any idea how i do can get it working and where to connect the leads??

Thanks
rbhammon!!