99 F150...

Mt gauge flickers like a strobe light for about 2 mins every two to three days and the completely stop glowing...my underbody glow kit stopped working...some of my lights don't work. And my gas meter always goes up to a half a tank..if full or on almost empty...

Any help? Fuse box maybe?

 

Whoa, you've got a whole bunch of problems there and they may or may not be related. As a big word of caution, attempting to diagnose electrical problems remotely (like over the internet) is very hard to do. Sometimes, you just have to be there. Be that as it may ...

Let's start with your "underbody glow kit." (I'm assuming it's neon and not nuclear powered.) This being the only problematic aftermarket thing that you mentioned on your truck, how did you wire it in to your truck's electrical system. Improper wiring can lead to all sorts of other electrical problems. I'd start by disconnecting it at the power source to isolate a possible problem.

The other (easy) thing I'd recommend is checking your fuse box(es) for blown fuses. Your Owner's Manual will tell you where they are. Try that, then get back to us.