Any way it could have gotten water inside? That is one way to blow them up.
Greywolf,They need to be mounted with the opening in the bottom.
this could be the issue i had a set of horns i transferred from bike to bike i bought in 2004. I finally gave them away with the last bike i sold.Greywolf,
I took it apart and couldn't save it. It was mounted the right way. In fact I once rode it a whole day in the rain and it worked fine after that. It was on my 09 Wee when I bought it used a year ago, but on close examination the horn looks a lot older than the bike. I have a new one on order.