Okay, I found and answer from Curt after reading most fo this thread -
"If your auto on/off is in the active mode (bottom of system setting page) then the blue light should go off, in the standby mode after ten minutes or so of no bass signal. So if you have it in the active mode it would appear you have enough voltage flowing to keep the light on. It doesn't take much as the input is very sensitive. This is not unusual. John was incorrect about the light blinking when changing presets. The only time the light blinks is when changing the volume up or down on the remote. You will see the preset number change on the opening page as you change them on your remote. If you're aiming the remote at the sub, they will change. Believe me, I've tested it many times.
Thanks and hope this helps.
But what do I do about it? If the light is on, does that mean the sub is on? What fix is there if I want the sub light to go off?