One may instruct a non-Jew on Shabbos to remove or deposit
items in a refrigerator even if a light will go on when he opens the
door. While the refrigerator door (and light) is open, it is also
permitted to inform the non-Jew that if no steps are taken to
remove or disable the light bulb, the Jew will be unable later to
open the refrigerator (as a hint). One may also instruct the non-
Jew to turn on and use hot water, even if doing so will cause the
boiler to cook more water. (Shemiras Shabbos K’Hilchaso 1:31)