The switch pictured is from a Dodge p/u. As stated the pull function is to activate fog lights (do those work?) You have power to the switch (it is lit) but it might still be bad. You remove the switch with a putty knife or trim tool, insert in bottom edge and pry outward. You can unplug it and take it to any Dodge dealer for a replacement.
As I understand the button on the Freightliner wheel is to flash your headlights/high beams.
I would be most suspicious of the steering wheel button or the relay it controls.
2013 Coachmen Freedom Express 320BHDS pulled by a 2005 F250 King Ranch CC
A rainy day camping is better than a sunny day at work.