I had just baught a used 02 Eclipse and noticed that when I was driving at night, the dashboards weren't on even though my headlights were. I checked the fuse box on the passanger and the engine compartment, all the fuses seem perfectly fine. Is it possible that the light dimmer is faulty?

Yes, very possible. Sometimes just simply disconnected for some other reason.
Are your tail lights working? They usually tie in together with a tail lamp fuse.