To ‘crank ___ up’ means to turn it up fast, and a lot! Things that are adjustable, like the volume of a movie or the strength of a heater, can be “cranked up”:

Crank the heat up! I’m freezing!

I love this song! Crank it up! 

Using this phrase shows enthusiasm.

You can also say "crank up the volume" or "crank up the heat":

When he watches football, he cranks the volume all the way up as high as it will go.