My horn goes off when I apply my left turn signal.

Hello, When components on the steering column begin to actuate one another, there is a great posibility of a wiring problem in the steering column. It is likely that the wire harness has rubbed away the protective coating, and is causing wires to connect where they should not. You'll want to look underneath the dashboard, and see if there are any bare wires that you can see on, or leaving the steering column. Damaged connectors or a damaged fuse block are posibilities, but inspecting the steering column wiring harness should find the issue.