Previous owner wired a aftermarket stereo system, then removed it prior to sale. Today I left my front windows down half way and it rained. Now the speakers are cutting in and put making spuradic loud crackling and static noises. Electrical is not my strong point. Only thing I can think to do is unplug the front speakers. Should I look into anything else?

 

Actions of previous owner unknown, if the removed aftermarket radio used the stock amplifier under the seat, or its built-in amplifier.
Disconnect +12V power or the whole plug to the stock amplifier under the seat and check if noise is gone.
The jack faces forward.