I am building my own 4th brake light to go in my receiver hitch. I'm hooking directly into the 4 pin trailer harness, but I'm having a problem. My light comes on with the brakes like it should, but it also flashes when the blinkers are on, which looks really dumb. I understand that it's flashing because the brake and the blinkers are on the same wire and use the same filament in the tail light assembly. I know that the hitch lights you buy in the store don't flash, so I took one apart the other day, expecting to find some kind of logic chip in there to keep it from flashing when the blinkers are on; nope. Intstead their connector has two wires hooked up to it; the ground and the right brake/blinder wire. The brake/blinker wire goes directly from the connector to the bulb. What am I missing? How are they keeping the light from flashing when the right blinker is on? (I thought about tapping into the brake light over the cab, but that's too much like work.)

------------------
-'97 F150 Super Cab XLT long bed, 3rd door, 4.6L 5 spd, 3.08 rear end
-Added:
Aiwa CDC MP3 stereo
Sprayed in bed liner
Bug Deflector
Ford Running boards
DRL's
K&N Filter
No Door Chime
Radio Delay
Fog Lights on w/ hi or low beams or parking lts.
Reese concealed hitch
Folding rear hitch step w/ attached brake light.
Pace Edwards Roll Top cover

 

I also have a receiver brake lamp. I purchased a logic circuit from J.C. Whitney for around five bucks. The wiring is fairly simple. The brake lamp won't flash with your turn signals. However, mine does flash with the four way flashers, which is nice for emergency situations.