ive just had a look at the diagrams to trace things. Although, bear in mind this is from a RHD motor, so yours may be different ***.
https://www.dropbox.com/s/skmqk4fx6kzq4pv/Fuses%20and%20Relays.pdf
The Dropbox in-browser viewer seems to mess up the diagrams and take ages to do anything. Open the link, then use the download button (top right) and select direct download. Open with your prefered PDF viewer
The speedo assembly is fed from two feeds. One permanent live and one ignition switched live. I suspect one of these two supplies may be missing, so lets try and find out where its going astray :s
Speedo Permanent live is fed from passenger fusebox *F12 (5Amp) fuse, which is also one of the feeds for the Body computer UCH.
Speedo Switched live is fed from passenger compartment *F8 (15Amp) fuse, which also feeds Transponder Ring and the Body computer UCH.
Unless you already used a multimeter, double check fuses F8 and F12 with a multimeter for continuity between the blades of the fuse.
With the fuses still removed, Use a multimeter with the black lead to chassis ground or battery negative, and use the red lead to check for +12V on one side of the fuse holders. The other side of each fuse holder will be what goes to the speedo so only one side will be live.
Permanent live for Fuse holder F12
Ignition switched live for Fuse holder F8
Being one of the easier connectors to get to, lift off the cover above the speedo (it lifts straight upwards).
Disconnect the connector on the rear of the speedo.
Put the fuses back in and check for voltage:-
Permanent +12V on the red wire (*Pin28)
Ignition switched live 12V on the yellow wire (*Pin21) with the ignition switch in normal running position.