'93 Grand Marquis light switch problem

If you replaced a module or connector, check the pins on the new item with a meter, they may not make the same connection as the old one. Also most electrical items on a car switch on the negative side of the circuit (meaning power is always applied, and a connection on the negative side completes the circuit), so an errant ground could cause power to be applied to that item. Without knowing exactly what you did and what the pin outs on the replacement item are it's impossible to make a suggestion to you, other than to review the circuit in question, and don't trust any replacement circuit item to be exactly the same as a new one. They love making year by year changes to wire harnesses, connectors, and modules.