Mark, we had a similar problem when our system was first installed. It was August, and I turned on the heat just to see if it worked. It didn't. It turned out that the company that installed the system used the wrong type of thermostat. Actually, they were aware of the problem an had just installed one temporarily so that we would at least have A/C while waiting on the right one to come in.
A light activates on my thermostat when the electric element comes on. It has been on often the past couple of weeks with temps consistantly below zero but I have never noticed lights dimming for any reason.
"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." Stephen W. Hawking
