Broken Brwn/ Lt blue wire under my 1988 Ford Ranger XLT under driver seat, can't find it in specs

Hello. My question is simple. Iam unable to find the broken brwn/ Lt blue eire thats located underneathe my driverseat floorboard of my 1988 Ford Ranger XLT. My truck is down. No dash lights. Battery good. But rund down when placed in compartment over nite to .1
Its a deep cycle battery. Recharges fine. I’m going to check the sending unit coil, alternator and ignitoon module sensor. I will be using a multimeter. I don’t have a ammeter yet but want to get one and circuit braker soon.
I just don’t want to repair wires without knowing fir certain where they lead to. I believe they may go to the ignition system. Thanx.

can you trace it physically on either end?

Maybe re-ask your question. If you can’t find the wire, how do you know what color it is? Why do you think there is supposed to be a wire in that location? If you can specify the function of the wire, that would help.

I have the factory diagrams for my 87 (should be the same as your 88) & don’t see BR/LB in that area.

Fuse 4 feeds the main light switch, which feeds fuse 17, which feeds a splice to the dash lights.

Fuse 4 is hot at all times. Fuse 17 is hot when the main light switch is on.

If the headlights come on but not the dash lights check fuse 17.

If the headlights do not come on check fuse 4.

Ground for the dash lights is under the dash near the steering column

I think there is a brown/light blue wire that connects the fuel pump inertia switch to the fuel pump relay.

You have not stated exactly how it is known the wire is broken but there should be 2 ends and a simple splice should fix it right up. If that’s the inertia wire then the fuel pump will not run and if that wire has grounded due to a break then it could be that a fuse or fusible link has popped.