Running lights and brake light issues

[KriegsReich]

I'm not even sure where to start. I bought the truck a few weeks back, and immediately noticed the rats nest of wires in the dash. There's been a lot of wiring done with stereos it looks like. And instead of taking the unused wired out, they just cut them and left them. It currently has a cheap CD player in it.

The heater controls (non a/c) have been spliced into a lightswitch (like the ones in your house) and it's obvious they were plugging it into the unfused ign. feed on the fusebox to run it. When I say the heater controls, what I mean is it appears they bypassed the actual control panel and have it running off of this light switch. When it it plugged into the fusebox I can get my front blinkers and running lights (including the two on the sides) to work, along with my rear passenger blinker. No running lights in the back or brakes whatsoever.

Other than that nothing is out of the ordinary by just looking. I've traced the wires and everything is plugged into something. I've done my best to look at the diagram and match things up but it's come to a point where I'm throwing my hands in the air. I see a few problems but I have no idea where to start.

Do the lights normally feed with the heater wires? I can get pictures of what's going on if necessary.

A friend told me to start checking grounds and I'm going to clean the two side running lights in the back because they are corroded to hell. Here are some pictures of the tail connections and a mystery wire... pretty sure the bigger one is stock and they've replaced the other. I have no clue what this little mystery guy is...

Anyone know what this is supposed to be?




And why are these different? My guess is the driver's side is something someone has spliced in.

Driver's side



Passenger's side
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