What was found
MAIN DOOR: REPEAT WRITE UP. AT ALTITUDE THERE IS A HIGH PITCHED SQUEAL COMING FROM THE MAIN CABIN DOOR. IT CAN BE HEARD IN THE COCKPIT WITH HEADSET ON AND IN THE CABIN. IF YOU ARE FACING THE MAIN DOOR FROM THE CABIN, IT SEEMS TO BE COMING FROM THE LEFT SIDE OF THE DOOR OR LOWER LEFT AREA. IT SEEMS TO START IN THE 20,000 RANGE OF ALTITUDE.///SIGN-OFF///REMOVED AND REPLACED CABIN DOOR PRESSURE SWITCH. IAW CESSNA 560XL AMM 52-10-04. OPS CHECK GOOD.