jiggle the fuse, could be not contacting enough, check other connectors if you can get to them. Sounds like not enough amperage is getting thru the connectors to the horn. Also try to blow air behind the steering wheel horn switches? Jiggle them too. Hit the horn(s) with a mallet or lighly with a hammer, loosen them up, brand new and could be "stuck" on a "burr" or something.