I have a 2008 civic horn does not work i have a diagram of the fuses but i do not know witch relay is for the horn can anyone help diagram is not on fuse box cover under hood.

 

Owners manual likely to have image of fuse/relay placement. Start switching relays that match [many do] and see if horn works. If so, you'll find something else that won't [light, ac, door locks, etc]. Try alldata.com. they have some limited free access to the general public. I use the pro version. Tom