Where do you have the PWM cable connected on your RC? It is supposed to connect to one of the team color connectors. I'm thinking that you might have connected it to the PWM connector on the RC. They updated the wiring diagram to show where it connects. You probably don't have the new version. Get it here...
http://www2.usfirst.org/2007comp/oth...L_LIGHT_R1.pdf
Matthew