1988 Ford Mustang Draining Battery

I had to replacethe ignition switch because the old switch had begun to fall apart and the car would cut off during normal operation. As soon as I replaced the new switch my battery began to drain overnight and I noticed that the voltage meter warning light is on and the meter is reading as much as 18 amps during normal operation. I have not yet begun pulling fuses and using a test light or ammeter to check for the source of the drain. One thing unusual is that when I remove the positive battery caple while the vehicle is running the windshield wipers begin to operate on their own.