x2 on the grounds - Had spider nests in the 49 horns. Gave them a good cleaning - but I'd advise against disassembling too far. Like dgrinnan says, grounds are critical - in my case the little buggers had caused corrosion (affecting the grounding points) through the unit but I was able to clean and polish them back to life.
I ran a separate ground wire from the horn bodies as well and that's worked well.
