There are a number of threads about faulty speedos and dry joints etc. but none appears to detail exactly what to do. I managed to fix mine with very little effort and minimal tools and no soldering.

I cant guarantee this will work for all but its got to be worth a try:
  1. Remove steering column top cover - 2 screws underneath on lower cover.

  2. Remove 2 screws now revealed holding instrument cluster to dash.

  3. Gently draw out cluster removing 3 connectors from rear. 2 of these have a clip which needs to be released with a flat blade screwdriver.

  4. Manoevure cluster out from behind steering wheel. On mine it came out without removing the wheel but others have found it necessary to remove the wheel.

  5. On the bench remove the centre module held by 3 screws...


  6. Then carefully remove the centre module keeping it parallel to pcb sliding out the contacts. Place this to one side...


  7. Remove all the torx head screws holding the PCB on to the main moulding...


  8. Carefully remove the semiconductor (voltaage regulator?) from the blue connector...


  9. Remove the 2 nuts and washers from the holding the fuel guage...


  10. Seperate the PCB/Instruments from the main black moulding. Be careful of the various trip/clock knobs etc...


  11. To remove the speedo instrument from the PCB first unclip it next to the blue socket. Use small screwdriver to unclip...


  12. Finally remove the speed instrument itself as in photo. Again there are 4 contact pins so go gently...


  13. I reckon on mine these 4 contacts were the problem as they were a little grey and dirty. I used a very fine nailfile but a fine needlefile would be ideal to clean the contacts...


  14. In the same way I also cleaned the centre module contacts and semiconductor legs...


  15. Reassembly is reverse procedure. This was enough to get mine working again - hopefully it will work for you too!