need help with 12v black wire in a 7way connector

i believe on a KW that light circuit is controlled by a seperate dash switch,not the headlight switch.it may not have a label on it.good luck.

 

On my 99 KW, there is a gangle of fuses in weatherproof holders on the firewall (in the engine compartment) near the steering wheel area.
I have prior posts here explaining it. I too had a similar issue and all of my circuit breakers were good. I had no power leaving the cab.
In my case, it turned out to be a 5A blade fuse in one of these weatherproof holders. I would have never known about them and dont know what all 4 of them really do, but why these are separate vs in the fuse panel - I cant explain.

If you dont know what your looking for - you dont even notice these.
Im not saying this is *YOUR* issue - but something to at least rule out maybe?

 

with a truck that old one can only guess how many times that wire has be swap'd.. I had a T2000, and the 1 and 11 o'clock positions on the pigtail were tail and marker lights.. i rewired the dash so when i turned on the marker lights the tail lights would come on also, and used the tail light switch for the dump valve on the flat bed i was dragging at the time..

now i'm rolling in a t660 and as before, one wire is for the tail lights of the trailer and the other is for the markers.. why the factory just don't use one wire for both is beyond me.. it would open up a wire for something else, backup lights, dump valve, lift axle, strobes.