How can I put the sun off completely?
I changed Azimuth and Elevation to 0.000, but unlighted regions are still not completely dark.

Put this in your script:
sun_light = 0; // no sun

I have a look at the manual for 2 seconds and find that:

sun_light = 0; // no sun

Oh, sorry.
Thought I did this with puting elevation to 0.

But there is still a bit of light. Am I doing something false.

Now I found the solution for myself, but thanks for posting.