3rd brake light won't power OFF

Hello everyone. I recently did a cab swap and I'm working out the last few bugs. PRIMARY issue is that the turn signals activate just fine. However once I apply the brake pedal, the turn signal goes into hyper-flash.

I do have a single, black wire that travels down the DS A post (with 3 other wires) that I cannot find where it connects. Also notable is that when I plug in those 3 A post wires, the third brake light comes on...and stays on.

Any help is appreciated --I'm losing patience with this.

 

May have found the issue. The wires traveling to the 3rd brake light are from the 1998 donor cab. I imagine my 2003 wiring harnesses is not going to match up nicely. .....old wires went out on the scrap trailer.......uuuggggggg

 

I can maybe help with wire diagrams.
But I can not promise I'm willing to stick it out and do the rewire with you.
That's a lot of work.

 

Does that 3 wire plug look like this?

 

Yeah man......
It's different......
Notice how the 2003 comes in on the IG1 connector at pin1?
Then notice that the 1998 comes in on pin1 but back out on pin2 to ground?
Yeah that pin2 on the 2003 is used for the interior cab light.
You can make this work.....But you need diagrams. And time. Lots of time.


20031998

 

That 3 pin connector is the one. I used a meter on it today, and if I remember correctly, the middle pin is hot constant.....the outer pins go to ground....that is on the 03 side.