Sorry for the late reply.
Your headlamp dimmer switch and turn are part of the same multifunction switch, correct. The problem may be either that switch or the wiring in steering column. As far as turn, what about the combination flasher?
You can check circuits into and from steering column, with proper wiring diagrams. For the system in question, if voltage into the steering column and none coming out when system is activated, the problem is somewhere in the steering column.
I realize this is an old post. You may no longer own this vehicle. In the future hope you don't have any vehicle issues, but, if you do, keep the site in mind. They are always working to improve the site and it's free.
Have a good day.
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Sunday, March 29th, 2015 AT 2:26 PM