Cadillac Seville / Cadillac Eldorado Forum Discussion, Trunk deck lights problem,,,1998 SLS in Past Cadillac Vehicle Discussion; On my trunk deck,,there are four  lights two  per side,,,had a light out ,and went to replace it,,it ...
On my trunk deck,,there are four  lights two  per side,,,had a light out ,and went to replace it,,it was rusted really bad,,of course it broke ,and I had to use needle nose pliers to remove it,,the socket was damaged so I replaced it as well,,,after installing new connectors and bulb still will not work,,after checking the wiring with a tester ,,,no power to it,,,I have the original owners manual,,look for possible fuses but unable to locate it,,DOES ANYONE KNOW WHAT THOSE LIGHTS ARE,,And also its the only ones that have conventional push and turn to lock,,the bulbs have a round metal base with 2 contact points,,the ONLY ones like that,,,help please
If the bulbs have a bayonet base, 2 contacts, they're probably an 1157 dual filament bulb but only 1 filament is used - the low "parking lamp" filament. I think the wiring could have been set up for the Export model which used amber rear fog lights..........N*Caddy will know.
Anyway, not only does the trunk mount light wiring harness tend to deteriorate, it also chafes where the harness leaves the left trunk hinge wiring channel. Check that and the ground lug at the left fender inner body stud.
ALL of these Sevilles have a weird combination of bulbs and sockets - you just have to figure out what is what. I do know that the inner (trunk) lens bulbs are running and tag lights - brake filaments are the outer assemblies. Does your car have the clear backup lights on the trunk or in the outer assemblies ?.......... My backups are in the trunk setup, so that one panel/lenses takes 2 #1157's, 2 #3157's, and 4 #194's, not including the 3rd brake light assembly.
EDIT: You might get some ideas from the Osram/Sylvania automotive bulb website - enter your car and model and you get a list of what bulbs go where.