2007 Chevy HHR's horn only works once in a while. What can be the problem and how do you fix it?

Also, one of the keyless entry remotes stopped working around the same time that the horn stopped working -they (my grandparents, owner of the vehicle) thought that had something to do with it, but I couldn't see why. It was wrecked on the driver side, front tire area in 2008 but I believe the horn was still working after all the repairs..this just seems to have been happening within the last year.