last night my exposure revo decided to stop working .
I have tried two more wires , so it not that.
does anyone know how I can test the light on its own ,or the hub,
so I can send the right part back and hopefully wont have to strip the wheel down

Is it connected up to charge anything? That would tell you if the hub is working.

I would guess it will be the hub rather than the revo...

I'd call the Exposure Service team really helpful

its just on the light ,
I didn't get around to connecting anything else

Whereabouts are you? Be easy to check another Dynamo wheel in and see which it is...

not much to check on the lights. First check your connectors on the hub, when this happens
Trim back the wire ends give new fresh cable (& better connection) that's what solved it for me when I had the same issue