When I turn on the car lights, the gas guage drops to empty. if I turn the interior light switch all the off, the gauge goes back to normal, but i have no guage lights. Short or what?? thanks

some ground problem...

Do what i did, first take a set of alligator clips and attach a set to the back of the instument pod then one to the body of the car. This should ground the cluster then try the lights. If the gauge stays ,then its a ground. You can then try to find the bad ground area or just make your own one up. Some times the ground bar could be missing if you had the dash apart at one time....

Check your fuses first. It also could be a lost ground connection.

I had the same problem. I ran a ground from the back of the gauge cluster to the firewall. Problem solved.

Thanks guys, I hope to check this weekend. Next is the tail lights. three of the four dont work.

That's probably grounds too. The tail lights get their ground connection from properly seating the sockets in the tail light housings. Clean them and seat them well.

And the tail lamp housings benefit from grounds too, since they are isolated from the body by a thick gasket.

I had my tail lights totally rewired, used FORD (yes, Ford) sockets, they are metal and dont fall out as the plastic GM`s do, and hardwired/grounded them)

The best money I've spent for both of mine... The repop trunk wiring harness at about $100. It saves countless hours cutting, splicing and soldering. Been there, done that and done it again.