Back brake lights

Ok here is my question: when I press on my breakpedal my tail lights comeon at the beginning of the cycle then they cut out and then come back on at the end of the cycle, what could be the problem?(I have tried a new back brake switch)and I still have the problem. Oh I forgot to mention that when I first start steppng on the brake I hear a click comming from the front of my truck under the hood.