Interior lights will not turn & all windows won't roll down but there is nothing wrong with the fuses?
I don't think there is a fuse, it may be a breaker on the 99. The switch could be defective, here is a video on how to change it if it is...https://www.youtube.com/watch?v=nV3s9T4MOWo
Search Cadillac DeVille Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Cadillac DeVille Experts