a ground on the signal unit would depend on the unit, but there's no reason it would be needed, the unit just transmits power to the lights, which have their own ground
the horn button supplies a ground to activate the horn, the sparking would indicate to me you need to check the condition of the button parts and wiring ..... also, the year is relevant, and whether it has a horn relay, they're wired different .....and no need to yell
Bill
