There is a green LED to the right of the off switch on my ACC contols, this is not the off switch LED, as this is on the left of the switch.
I hadn't even noticed it was there until the other day when it came on.
Any ideas what it is??
I thought the same as you. What is this for. One day it came on and I found myself working out why.
It seems to come on when the ACC detects a fault in the system. The system does tend to lie about faults though as it will usually correct itself.
Best thing to do is put the key in the ignition, and turn to the ON position but don't start the engine. Simultaneously press AUTO and vent (looks like <-->) for about two second and let go.
This will start the diagnostic procedure and also reset the system. The numbers on the display will go from 0-5. If it stops on a particular number then there is a fault. Im' not sure what faults the numbers relate to, but I'm sure some one will.
It's done it about 4 times in 18 months on my car and each time the car has corrected itself within 24 hours of me performing the diagnostic reset thing.
Hope this helps,
Toby Field (UK)
'93 9000 CSE 2.3T Auto