I am assuming the signal light switch is kapoot, but I want to be sure before ordering a new one. Here is the story: The left front signal light light is not flashing and the left rear is. All other lights work. I traced the white with green wire from the left front signal light back to the steering column. With the left signal light on there is no power to my test light where this wire comes out of the connector to the switch. [Tested both below and above the connector] However, my test light flashes when I place it on the wire going to the left rear at the connector.
Also the horn won't blow with the key on, only when key is off.
A faulty signal light switch for sure? Thanks in advance.

 

Check ALL the bulbs on the non-blinking side of the truck. If one is out, none on that side will flash.

The horn problem sounds like a bad relay (if you have a tilt column or cruise buttons), or a bad ignition switch. Find the post about ignition switches in this thread.