I need help I have a police interceptor when I turn
my headlights on after about 15mins they shut off
and the dash lights start flashing and theres a loud
buzzing I have been told it could be a short in the
wires could be the headlight switch but I'm unsure
can anyone tell me what I should do or what it
A short would lead to a blown fuse, an "open" would lead to a non-working light. Your problem sounds like something else, namely a light control module problem. Model years later than yours had been recalled for a very similar problem (https://www.consumeraffairs.com/news/ford-recalls-older-model-crown-victoria-and-mercury-grand-marquis-vehicles-010416.html). The LCM is mounted under the dash, in the area above the gas/brake pedals. Pull and reseat the wire harness to it and see if that fixes the problem, if not a new LCM may be in order.
Try and get battery and alternator checked before u buy anything umay have a dead cell in battery or one of those could be shorting out causing your battery to go dead