'92 mercury grand marquis wipers don't work, headlights blink on and off, power windows don't work, a/c don't work, battery keeps dying.

Well Angela the only way to find out why these thing's are not working or not working correctly would be to do electrical testing ! Find wiring diagrams of the affected circuits an get a DVOM - digital volt ohm meter . Do you know how to do basic automotive electrical testing ? How to use an read a wiring diagram ? Voltage drop testing ? Your battery dying , depending on when it dies , over night or while driving would need different testing procedures .
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http://www.bbbind.com/free_tsb.html you can find wiring diagrams here . Watch the videos , buy a volt meter , do some testing ! Good luck