Then i did what any tinkerer would, and took the whole unit to bits
The instrument housing itself is in 2 parts, which after removing the screws that hold it together,it all comes apart quite easily. If you find that the ends will release one at a time but as soon as you open one end the other clips shut again then you will have missed the final screw that goes through the middle of the PCB into the front section (see green arrow in picture) i learned this by applying more force than i should and broke the lug off
Once the front section is removed the instruments then simply lift off the back section, and once youve done that, you can see that the dials locate onto pins that come out of the rear section, which is circled in red in the picture.
Logic told me that these pins must be the power supply to the dials as well as just locator pins, so i cleaned them up with a small amount of contact cleaner spray, as well as spraying some into the back of each dial as well, and just in case this wasnt enough, i decided to slightly (and very gently) bend the pins so they were more of a snug fit when pushed into the dials.
I finished off by applying a thin strip of blue tac around the inside edge of the front section so it would space it out slightly, thus pushing the dials harder down onto the pins on the rear section.
I then put it back together, refitted it all and hey presto, every gauge working absolutely faultlessly.
The picture isnt the clearest, and i really should have taken more in order to make a better step by step, but to be honest i had no idea whether what i was attempting would work or not, and i was quite expecting to either make it worse or break either one or all of the dials completely.
I hope this can be of help to some other 406 owners anyway
