that is probably the circulation fan to blow heat in the room
first...see if this is your unit -
Ok we know for sure now that it is a millivolt problem. Only thing is which. We bypassed switches and went straight to valve. So now if you had a meter we could see if the generator is coming up short.
Or you could get a thermopile since the greater odds are with that. Price is anywhere from $25 bucks on up - http://www.thegreathardwarestore.com/ProductDetails.asp?ProductCode=789925&click=2744
Sorry for the long way but at least now we got it to one of 2 things.
do you have a tab or wire u nder the thermocouple on the valve?
Thanks for the update Bob. I am glad all is well with the fireplace. Something tells me you know you way around it pretty good now!
I admire your perseverance. Happy Holidays!