I watched it last night. I started it up and it made it through two complete cycles. on the third the room temp fell below the set temperature and the service call light came on and nothing.........but I did notive a light come on inside the control box. It looked either green or yellow, I cant be sure.....this model has the gray plastic control box, not the newer clear one. The red and green lights are on the outside top of the box. but this light was inside. I never noticied before.