Firstly I put this here rather than in technical as I'm not sure anyone beyond Europe will even know what these are ? If I'm wrong, I'm sure an Admin will be along and move it in good time :-)
So my PSI3 developed a fault over a few weeks, before it became unusable and needed to be unplugged. Initially it started displaying the odd random character in place of the correct character or blank. Over time this became progressively worse until on one particular day on getting into the car all the psi3 showed was animated hyroglyphs, with no apparent correlation to the expected output. It was however still functioning as the shift light was still working.** It was suggested that it may be as simple as a dry solder joint on the display module.
So at that point it was unplugged awaiting some time.* I finally got the time this week, and popped it out and took it apart to see if it was salvageable.
So having dismounted the unit, it has only 8 fasteners apparent. 4 on the front, 1 on each side and 2 on the back.
The back ones you can leave alone (they simply mount the rear socket for the 2 plugs), and the front ones (Allen screws) can also be left alone for now.
To disassemble the electronics from the case undo the single screw on each side of the case, then grab the front piece and ease it forward. Keep pulling forward and it should come free. I did find that I needed to ease the case a little as it was slightly bowed. You can remove the 4 allen screws on the front if you wish to avoid damaging the front piece, as this will give access to 4 metal hexagon extension pieces you can use to pull the circuit boards out.
Having got the insides out, then disconnect the ribbon cable by opening the clips on each end and then pulling, this disconnects the ribbon from the main circuit board* and leaves the ribbon connected to the plugs in the back of the unit.
Having got this far I then dismounted the display board, this simply requires 4 plastic pins to be squeezed at the ends to pop them back through the board, then lift the daughter board off complete with the display.
All the pieces out it looks like this.
I then resoldered, all of the pins that mount the display to the daughterboard and put it back together.* All now working OK again.
While I had it in pieces I also added a layer of yellow acetate to the back of the front plate, which has converted the display from blue to green so is more of a match for the green illumination of the dash in general.
In true workshop manual fashion, reassembly is the reverse sequence of removal :-)