Taillights and Dash lights not working, 1996 B3000

[Linus72]

I've been trying to figure this out for awhile and could use some help!
So far I've checked all fuses underwood and at fuse block in cab, I replaced headlight switch but that didn't help either.
I've heard it could be the dimmer switch?
I've also heard the dash lights and rear tail lights are connected?
To be clear, my head lights, turn signals, brake lights and front marker lights work But no dash lights and no tail lights.
Also, the lights where the climate control is do work and the radio lights dim when I turn on the lights.
So, any ideas what could be doing this?
Thanks!

 

[RonD]

Yes, the dimmer for the dash/cluster back lights but if the climate control lights work, i.e. dim and brighten then could be wiring issue at the dimmer
The dash has 6 bulbs, 3 bulbs use a different wire to dimmer than the other 3 bulbs so with a wire issue you wouldn't lose all 6

Yes, fuse 7 in the cab fuse box is shared by Park and Back lights(cluster)

But all 4 corners park lights use the same fuse, there is no front back separation

If you have Keyless entry(fobs) then there is a Park Light Relay, so lights can be flashed for lock and unlock
But it is used for all 4 corners no front back separation

There is a Brown wire used at all 4 corners for park lights, I would test at the rear of the truck under the bed where "trailer lights" have been installed, wires can break there, there is just the 1 brown wire and it splits to the two bulbs AND license plate light

 

[Linus72]

Ok thanks I'm gonna check...I'm pretty color blind though lol.
I forgot to add I have no tag lights also.
The white lights at top back of cab don't work either but the brake light in the middle does.
Are the white lights at top back of cab also in same circuit as tail lights/tag lights?
Thanks

 

[Linus72]

Here's a couple pics.
There's a couple tape jobs there but how do I get to the one in pic #1 where it's behind the bumper??
I need to pull the harness down to access or how do I do it?