Im' having a lot of issues with my 2004 F150 5.4 on the instrument cluster.
First the 4x4 lights started blinking 3 times for a few days, then ABS light came on, then wrench light came on with P2106, then brake light came on, then check gauges came on, now tach and speedometer comes and goes as well as battery. Everything lights up. The dash looks like a friggin Christmas tree. I've been at idle watching all the lights come on, go out, come on go out.

I had a buddy hook up a Snap on scanner, and he couldn’t communicate to the PCM, ABS, and 3 other modules…
I'm not getting any tach, gauges, etc. I pulled up the covers on the floor board to expose the wires. They're all covered in water. Nothing seems shorted or broken. I found a ground wire by the emergency brake, it was attached to the side panel which was rotted. I relocated that, but it didn't fix the issue. I got a lot of rust and some rot in that area.

The dash comes on and off without touching anything. I was driving to work today, and the Tach and Speedometer would pulse - come on, go off, come on, go off.

I can't find any wiring issues anywhere. Took every harness that I found apart and they looked good to. Grounds look good.

 

That's a symptom of what's wrong. For whatever reason, the interior wiring is flooded and has likely gotten into electronic modules.

Your problems are going to be on par with a flood-damaged vehicle. You're going to need to stop the leaking, dry everything out, then find and fix whatever the water damaged. It won't be easy or cheap.