pop out the light assembly with a screwdriver and change the bulb. your receptacle may be taking in water at the car wash. duct tape over lens before going through automatic car wash.
your local auto parts store should have a guide to replacing. or look in your manual
Bulbs, switch or wiring
To change the bulbs all you have to do is put a flat blade screw driver on the right side of the bulb housing and gently push to the left. This will release the catch holding it in and it will drop out and down on the end of its wiring connector. 1/4 turn the bulb and remove. Replace the bulb and just put the housing back into the opening left side first, then just push up on the right side till you hear a click. Takes about 1 min per light. Works for all Deville types 00-08 The only place I found replacement bulbs besides the Cadillac dealer ($32.00) for 2 bulbs was NAPA Auto Parts ($5.00) for 2 bulbs, On my 2004 Sedan Deville the release is to the left side of the housing.
There are actually 3 bulbs (GE #1141). On my De Ville there is a small compartment on the rear dash directly in front (from inside the car) the high mount brake light. Simply open the compartment and pull back the trim exposing the 3 bulbs, replace any or all nonworking bulbs.
door button stuck --bulbs? fuse.
There are two (2) bulbs. Gently remove the plastic lens, sometimes there is a slot for a very small flat tipped tool (screw driver) to remove lens. You will then see a white plastic clip, gently push to the side and pull down this will remove the bulb casing. Twist the bulbs out. If you purchase auto part bulbs, you must bend the two electrical wires to the sides of the bulbs or they will not work. Cadillac soldered the bulbs into the plastic holders, but it is to the side not the way the bulbs come. Otherwise you will need to purchase the bulbs from a GM dealer.
: To change the bulbs all you have to do is put a flat blade screw driver on the right side of the bulb housing and gently push to the left. This will release the catch holding it in and it will drop out and down on the end of its wiring connector. 1/4 turn the bulb and remove. Replace the bulb and just put the housing back into the opening left side first, then just push up on the right side till you hear a click. Takes about 1 min per light. Works for all Deville types 00-08
push up and turn on the housing
You need to remove the liner on the trunk lid. That will give you access to the license plate lights housing. Remove the sockets by twisting 1/4 turn and replace bulbs. Size for bulbs are 2825
i got a 1993 Cadillac Coupe Deville and my turn signals was doing the same thing and I got new bulbs and still didn't work. I had to get a fuse to make them work
If you can not remove fasteners on outside, you may need to cut a section out of the inside of trunk to get your hand by the bulbs.
The clear covers for the license plate light bulbs have small arrows pointing in one direction. Simply push the cover to the direction of the arrows and the covers will slide off allowing for the old light bulbs to be replaced.