The defrost timer of my side-by-side refrigerator is not working. I have
ordered one but it'll take a week to arrive. In the meantime, I use a
screw driver to manually switch between the cooling and heating cycles.

I notice that if the refrigerator stays on the cooling cycle, the
temperature of the refrigerator side (as opposed to the freezer side)
seems to rise. In other words, the refrigerator needs to go through the
heating cycle for the refrigerator side to get cool.

I wonder why it is so.