1989 Vette Conv. Courtesy lights stay on and the battery runs down. Necessary to pull fuse when parking it. Replaced timer, didn't help. Checked headlight switch, seems to be working fine. Would appreciate any suggestions concerning how to repair this problem. Thanks

Look to the little pin switches at the fron of your door opening (on the body/front pillar). They are the ones that the front of your door pushes in to open the contact and turn off the lights. The center has a bad habbit of pulling loose of the plastic wire pin holder and no longer getting them to separate leaving the lights on. Push each one in while door is open the one that doesn't turn off the lights is your broken one. Unscrew it and gently pull toward you to verify.
Good luck.