Show me the speed!

So, my original Smiths speedo hasn't been working properly for a while (OK up to 40mph, then won't go back to zero and so you end up showing as doing 140mph, with the odometer going up in unison). So time for a new speedo...

I decided I wanted a GPS controlled speedo which means 2 options; a £50 Chinese item or a £250 unit from someone more trustworthy (there is honestly nothing in between) . Normally, I'd go the cheap route but the cheap ones don't have a trip meter and I use that all the time because I can't trust my fuel gauge. So the expensive option it had to be... Speedhut in the US do an infinitely customisable unit, so that's what I went for.

It arrived a few weeks ago and wasn't quite right; the blue of the dial was much darker than their website showed, making the silver numbers not very legible. But I couldn't be bothered to wait weeks sending it back, so it will do:

It does feel very good quality, solid and well made. Fitting it was fairly simple; first, remove the old dial and widen the hole slightly:

The wiring should have been simple (but see later) - 12v ignition, earth, dial illumination and a permanent live feed for the unit to store GPS data so it gets a quick signal the next time you start up. The permanent live was a simple wire direct to the positive terminal of the battery and I decided to reuse the plug from the old Smiths dial - I had the original wiring diagram it came with, so it should have been simple - snip the 3 wires out of the plug I needed (for some reason, it has about 7 wires, most of which aren't used), fit terminals and job done.

I've recently rewired my dash to make it easily removable with plugs for all the wires - the problem here was the GPS receiver has to go on top of the scuttle and I couldn't easily make a plug for the special coax cable it uses to connect to the dial. So I had to fit the unit so that it comes away with the dash, rather than being permanently attached to the scuttle. This required a little bit of jiggery-pokery - first a slot in the ally that the dash bolts to:

Then a piece of steel 3Md to the scuttle (because the magnetic GPS receiver can't stick to the ally scuttle) :

And now the GPS receiver attaches to that and its cable slots behind the dash - visible but not too horrendous and means the whole dash can come away:

Sadly, on a test drive, the darn thing didn't work, I think because I used the wires from the old Smiths wiring plug for the power and I guess the generic wiring diagram is incorrect (green wire for the +12v did seem a bit weird now I think about it). So I need to redo the wiring using my known 12v ignition terminals. I'm pretty sure the dial itself is fine because the illumination does work, so it's just the main power.

Hopefully have it working next time and I can play with the built-in 0-60 timer 😉