The issue applies only where the chachamim were specifically concened. One area of concern is performing acts which require seeing something well, like reading (Shulcha Aruch O.C. 275), where the chachamim were concerned we may inadvertently add oil to the wick to burn it brighter. There is a machlokes brought in the Mishna Berurah whether a heker works.
We are lenient in this law, certainly when using non-adjustable lights, since there is no gezeirah that one will come to light a lamp (probably because that takes more time and one will remember he may not do so).
As far as adjustable lights (dimmers) I don't know.
Fans do not fit into the reasoning, nor was there any such gezeirah.