Do you have a cap on the passenger headset cable connector down by the left side on the chrome rail? When mine got wet it squeeled. First noticed it after giving her a bath. Shook it out real good and it quit. I found a connection unner the seat with a cap where the cable plugs in to run to the passenger. Didn't need it there cuz the cable is plugged it...

Pulled it off and stuck it on the connector by the seat. No more problems under any conditions.