best to whats called center servo b4 connecting horn. Plug servo into rv the power it on.b4 that remove any servo trims and set endpoint to 100% install horn and linkage.. now do the right turn left turn same setup .you'll need 2 objects .turn steering full right make turn at outside edge put 2nd object now turn truck around do left turn so you adjust endpoints so you can do exact angle both left n right..