1988 Pontiac Firebird no electrical at all except rear hatc

Start at the battery check the wires and grounds to make sure there is not a broken wire, under the hood there is a junction box, it is on the drivers side over the inside fender well this contains 3 fuseable links, some vehicles has only two fuseable links, check to make sure you are getting power to both sides of the links. They look like just a piece of wire with a shield on it, it also has a few relays that control other things like the headlight doors. Check to see if you are getting power in and out of the this connection box. This box controls most of the major circuits going to the car but not all of them.

Check the relays to see if you are getting poer to them, they are under the hood where the fuseable links are. Did you cgheck the violtage going to the box and the grounds.