What an actuator for a Chevy Blazer looks like.

I have a 2000 Chevy Blazer w/ 134000 miles on it. Recently the car started switching into 4wd lo w/o me touching the button. I can hear a loud click noise when I place the car in neutral and press the 2wd button, I can hear a loud click near the front right wheel. I was told it was an actuator that I needed however, the descrepency is where the actuator is located. Is it the buttons on the dashboard that I'm pushing that need replacing or is it on the passengers side near the floor?