tekonsha brake controller problem

ok I am about ready to pull my hair out. I installed a tekonsha voyager brake controller in my 2003 Tacoma leveled and adjusted it, then took it out to weigh trailer weight and it kept flickering on and off then finally nothing. I called etrailer and they said check for a loose connection or short. I checked everything with the circuit tester from the trailer brakes back to plug and up under the dash. everything had juice and all turn signals and running lights are working. When I checked the blue wire running from the back of the controller with the circuit tester grounded to the truck the light on the controller comes on when I push the manual switch or I depress the brake pedal, as it is supposed to, but when I remove the probe from the wire-nothing! Can anybody tell me what is wrong? I would really appreciate any help

 

check the length of wire leading from the blue wire back to your 7-pin. could also sand down a spot for a better ground?