I aquired this speedo with a box of parts with my part built car. Can anyone tell me anything about how it works. It say AST on the front. Any help on wiring, do I need any other bits etc. Thanks
Rescued attachment speedo.JPG

Yup. It's the one I've got. It used to be sold by Rally designs as their "Racetech" one even though it's branded AST.

It uses a variable reluctance sensor which needs a ferrous trigger wheel.

It does have a little adjustment via the black dial on the back but basically requires a 833Hz trigger signal @ 100mph. I made up a trigger wheel (CNC laser cut) which clamps under the rear Lobro bolts.

The clues on the back there.....

Trigger wheel



Sensor mounted