I put a 3rd brake light from J.C. Whitney on my tear. It's a stick-on type with a curved base that seemed perfect for a teardrop. The Whitney web site says it needs no logic board. It has 2 bulbs and 3 wires: one solid black (ground), one blk/yellow stripe, and one blk/green stripe. It comes with virtually no instructions for hooking it up, so I wired the striped wires to the turn/brake wires on my trailer, and black to ground, but when I turned on either turn signal, BOTH signals in the taillights would blink! The brake light never lit when the pedal was pushed. When I unhooked the 3rd brake light the signals worked fine. Apparently, it does need a logic board, but I don't understand why it never lit up for any function (stop, turn, taillight)! I tested it before I hooked it up - it worked. Anyone know what's going on, and how to make it work? One more thing; the taillights are LED's and the 3rd brake light is incandescant. Could the resistance be so much higher in the brake light that no current flows through it?