Dash lights and truck starting?

Okay so I have a 2001 Ford F-150 with 14k miles on it. It didn't start or anything at first so the mechanic replaced the gem module and the inside fuse box it ran great I parked it and it did the same thing no start. No dash lights. No fuel pump the doors were going crazy locking and unlocking by themselves. But! The dimmer switch in the car if I slide that all the way up until it clicks EVERYTHING WORKS?! The truck will start my dash lights up but my dome lights are always on. I really have no idea what it could be and if anyone has any advice on what it could be or what I could do I'd appreciate it thank you.

That is Very Strange. Look at a Lighting Schematic to see how it ties into the PCM. In the meantime, pull the bulbs that stay lit. You were really lucky to find that trick. Most people would change the dimmer switch. But I think that it's a symptom, not the problem. But it might be.

There mustve been some major issues with that truck if its only done 14k miles in 18 years