1996 mercury grand marquis.

under the dash there is a spring loaded switch that works my rear brakes. when i push on it. the tail lights come on. other then that they don't work. I have wired in a new one and the problems still there what do i need to do.

 

The stop lamp switch at the top of the brake lever is working, so you are saying there are no rear lights other than when the brake is pressed? Have you tried using the manual push/pull headlight switch and slowly moving it in and out while someone observes the lights? I am thinking what you are describing is possibly a headlight switch problem, a common issue with the GM's.