JCB 540 Cab sway not operating

I now have a JCB 540 2007 model to look after as well as all the other stuff where I work, it was purchased S/H not long ago and the cab sway did not work when it got here, Fuse, relay has power, switch seems good, does any one know of any common problems or where i should look next. the previous owner said it was a sensor and he had left one on the dash of the machine. I am on a remote Island and was not here when the machine arrived so this sensor is not to be found and the previous owner is not helping Thanks Max