Iím waking the car up after winter ready for Stanford Hall in a few weeks and found the horn had stopped working? Iíd push the centre of the steering wheel and could hear the relay switching but it would still not work?

On checking fuse 13 I found this had blown, replaced it with a new one and with the ignition on still the horn wouldnít work but once you start the engine all is fine?

Donít know why the fuse had blown time will tell on that but Iím sure the horn used to work without the engine being on?