Corner markers, tail lights, and dash illumination issues

['92Custom]

Currently my Ranger is my only vehicle, and recently it has developed electrical issues that make it unusable at night. Given that it is getting to be winter and days are short, I need to resolve this issue as soon as I can. I've been tinkering a bit at a time to figure it out but am now at a bit of a dead end.

Here's the rundown - all of this occurred in the last month or two. My real questions are at the very bottom of this post:

The first issue that came up was a lack of dashboard illumination. This was intermittent and could always be fixed by replacing one of the fuses. After a while I realized the taillights were going out at the same time as the dash illumination. Still, replacing a fuse would generally get me 1 to 2 weeks worth of use. I wanted to address the issue but am preoccupied with my responsibilities at a new job so I procrastinated.

Thankfully I am able to rely on public transit for my commute, because the issue got worse. Eventually the headlights went out as well. I had to push the wires back onto the headlight switch then they worked, but it seemed that every time I fixed the headlights the tail lights would go out, and vice versa. Eventually it got to where the tail lights and dash lights would not work under any circumstance, and the fuse no longer blows.

I decided to replace the headlight switch and harness and now the headlights work fine, high and low beams are good. I did an inventory today and my dash lights do not work, my tail lights do not work, and the four bulbs (two on each side) at the front corners of the truck do not work. I don't know how they differ in function but I think two of them would be considered corner markers and perhaps the other two are supposed to go along with the blinkers. I can't stated conclusively when the issues with those four bulbs started because I may not have noticed at first.

The only lights that do work are the headlights, the brake lights, the large rectangular blinkers in front, and the blinkers in back. The 4-way hazard lights activate the blinkers as well.

I took the dash apart today and poked around on the flexible PCB behind the gauge cluster with my multi-meter. I was not able to find any discontinuities, but I also was not able to test every track since it appears to be a 2-layer PCB.

I tested my new headlight switch and figured out that the brown wire and the light blue/red wire are supposed to work together for the tail lights and some of the other lights. So I turned around the fuse box to look at the back and found one fuse (10 amp on the left side) which has two light blue/red wires coming from the back. This is marked in the owner's manual as "dash illumination". I touched the little test prongs on the front of the fuse, and also the chassis ground, and was not able to get any voltage from that fuse, but the fuse is good. I tested it in multiple ignition positions as well.

Back at the headlight switch I tested the light blue/red wire and it is grounded. Next I tested the brown wire and it is grounded as well. I pulled out a tail light and the brown wire was marked as "minor", another wire was marked "major", and a black wire was marked "ground" (it is a dual filament bulb).

So if I am understanding this correctly, electricity needs to come from somewhere on a light blue/red wire to the fuse box, go through the fuse (which is good) and come out the other side. That power continues in a light blue/red wire to the headlight switch, where depending on the switch position it may have the opportunity to get on the brown wire. The brown wire continues to the tail lights (and according to my diagram some of the other lights in question as well), then after going through the bulb the electricity comes out and goes to chassis ground.

Presumably the problem would be before the fuse box, so I followed the light blue/red wire to the wiring harness and into the engine bay. From there I was having a difficult time tracing things because it's all wrapped up with flex loom and electrical tape.

So my real questions are this:

1) Where does the other end of the light blue/red wire go after the fuse box?
2) Am I on the right track with this? Or is there some other obvious explanation that I've overlooked?

 

[rtg143]

You should have power from fuse #10 in the fuse box feeding a tan/white wire, The headligt switch then feeds the light blue/red wire through the dash dimmer rheostat and fuse #13 to power the dash lights.

 

[feellnfroggy]

Common problem for our trucks I'm told, and the blame lies in the pigtail and switch. Replace the pigtail and lightswitch. And you my still have to fiddle with the switch to get them all on at once. Have you recently (wthin the last year) wired up trailer lights? Check the ground. That's what burned out my ground wire on the light wtch.