blue box question

I am using the blue box and never noticed that it had a light on it until someone told me about it today. He just installed his turbo kit, found out it want running right, and emailed me with a question about the blue box and the green light on the corner of it. His isn't lit at all. Mine blinks. My car runs great so I am thinking it is correct.
Is the light supposed to be flashing, steady, or what? Thermal? thanks