Q&A

 Master

Check all of your left turn signal bulbs and sockets. There may be a bad socket or defective bulb. Do you use a trailer hitch? If so be sure to check the wiring for that as well.
If the bulbs check out then you will need to locate the short that is blowing your left T/S bulb.

here is a source for the wiring diagrams:

http://bit.ly/mitchell_repair_manuals_online

you dont have a truck like that