Hey folks.. I just bought a 93 civic lx as a 2nd car. I noticed that if my headlights or parking lights are "off," and I hit the brake, my license plate lights light up along with the brake lights on the trunk lid and back of car. STRANGE!! However, if my parking lights or headlights are "on" all lights on my trunk lid go out including plate lightswhen I apply brakes.My license plate lights actually go out along with the brake lights on the trunk lid. The lights on back of car continue to work properly...Why wouldmy plate lights have anything to do with my brake lights??Any suggestions?

 

Bad wiring while someone was trying to fix something? Maybe when it was in the shop at one time? Could also be some kind of short.

 

This is actually rather common. It happens because the brake light bulbs are not grounded. When the brake is pressed, the power that is supposed to light up the brake lights and go to ground, instead goes thru the other filament in the bulb and into the tail light circuit instead.

 

Ok. I changed all bulbs. Put in brand new brake light bulbs, and all parking lights and lic. plate lights. Still have same problem. What do you suggest? Thanks in advance!! Someone told me it could be a bad brake light switch? But I dont think that would cause the lic plate lights to act crazy like this!!

 

Check the ground wires in the trunk. I think there are several black wires that go to a bolt near the hinge on the left side. Remove all the brake light bulbs (the ones on the sides, the center brake light is apparently fine) from their sockets and test with a meter that the outer shell of the sockets are connected to ground. Take all the bulbs out at once, it won't work to test them one at a time.

Edit: Also while all the brake light bulbs are out, the license lights should NOT come on when you press the brake pedal. If they do it could be something other than a grounding problem.

Reading your original description again, it seems almost certain that the ground wire to the lights on the trunk lid is broken. It's probably in the section where it flexes when the trunk is opened.