Timbers

I have a 2015 GMC 2500 HD I have horn issues. I was working then it started to weaken...then it stopped working. Now it started to work again but very weak. The dealership said it would cost me an undisclosed amount because they are not sure what the problem is. I've read several complaints about this issue on the forum's and find it hard to believe that they have not heard of this issue.....that is what they told me. Ant advice would be great. Thanks