6V horns can work reliably for years on 12V. I'm not sure why you guys are saying otherwise, I know a lot of vehicles that have them, and I just hooked up my 6V horns on my 46 (Factory dual horns and connected to 12V). It sounds like there is a ground and/or contact issue with the horns.
Last edited by 46gmcpu; 07/19/2013 10:10 AM.