Although I have never had one, I would think that you need it mounted down on the dash. If it's up around the visor it can't pick up the light from the traffic signal. There is a hole in my dash right behind the center of the windshield and my speculation is that is what might have been there some time.
EDIT: chalk this post up to my misunderstanding that I thought you had one on the one ton.

Last edited by FriedGreenTmater; 11/01/2011 6:03 PM.
1953 Chevrolet 3600
Fried Green T'mater (Vern)
In the Stovebolt Gallery
Caution: Political Statement
Man who runs in front of car gets tired, man who runs behind car gets exhausted.