1985 crown vic not holding charge
battery sulfated and draining threw itself ,or a draw from a component of the car
Take the battery out and have it tested, if it tests good then you have a draw in the electrical system, glove box light, trunk light, alternator, stuff like that.
I've got an '89 LTD C.V. and it's the same as an '85. An '85 LTD Crown Victoria has an electric digital clock that is running constantly, It also has a computer with a memory that is on all the time. It should also have a motion activated dome lights that go on when the car shakes from wind or if someone lifts the door handle. Any of these can kill a weak battery overnight . A battery that has run down completely in the winter time can freeze overnight too and the plates in the battery will buckle or curl causing it to never being able to hold a charge ever again. Have the battery checked at an Autozone or Advance Auto parts store. They will check it for free. They will take it out of your car and put an electrical load on it to see if it's any good. If not good, then replace the battery. They will do this if you purchase the battery or not. If the battery is still good, They can also check if there is a draw on your good battery. A good fully charged battery will not go dead overnight if the clock is running but might if the domelight stays on overnight. Those years Crown Vics had driver's door domelight plunger switches on the door jam that stick and go bad over time. Mine did the same thing. Have someone check that too. It's probably one of those items but more than likely the battery needs replaced. Let us know what you find out. Good Luck, MrBlueOval/Kenny.
I agree, start with the battery. I work nights, and I can run my radio and lights for 12 hours and still have plenty of juice to start come morning. Of course, to allow for that I run an 1,100 amp battery with a 200 amp alternator. Also, check the condition of the battery cables. I am betting that they are getting ragged unless they have been changed, and I mean all 3. I use noting but 1 gauge wires on my cars, and never a problem.