[Roxo]

I have found by increasing the size of my Battery cables everything works much better. My horn always seemed to be be weak, lights also would get brighter as I revved up the engine. I discovered this when I moved my Battery to the bed of the truck and went to a 00 cable. My horn blows strong and the lights are brightest even at idle. At idle horn sounds strong even with all lights on.
Check Battery connections, cable size and Ground connections.