OK so here is my eloboration.
As I said before it seemed that the speedo was getting current because the needle flicked when the ignition was turned on and the kilometers were showing on the display, but not updating. For this reason I did not suspect fuses.
This morning I went to the car to remove the dash to check for any loose wires but the only screwdriver I have with me is too big for the tiny screws that hold the plastic under-dash panel. I then noticed that some other dash functions and the fan were not working. Hmm! time to check the fuses. Naturally I checked about 10 before I found the culprit, a 2.5 amp fuse. Replaced the fuse, a miracle the speedo was now working. I turned on the fan, great that was working too. I changed the fan to high speed - phaff! Fuse blown. I replaced it again - same result.
So I can run the fan at low speed but until I pull the dash I can't use high speed. I suspect the problem may be that reported by another TMer; ie. that the back of the fan switch or the heater switch or somesuch has cut through the insulation on the fan wire, in this case the high speed circuit.
Anyway something to keep in mind: the fan, the warning lights, and the operation of the speedo are all on the same circuit. The lighting of the speedo, the display, and the start up flick of the needle when the ignition is turned on are on a different circuit.
Peter, very interesting!
I found out the expensive way (Recovery to Williams) that on the Roadster all the functions you mention are on one 5amp fuse and if it blows the engine also will not start. Not sure if it will continue running if already started.
Yes, just one 5A fuse. I now carry a spare.
