So in the Jastram Main processor box, the Orange and Red on #42 and #43 are removed, abandoned and tied off to the side and the black jumper is installed in their place. Doing this bypasses the Jastram/Garmin Auto Pilot interface. The interface on 90r 03 was located aft of the starb engine on the aft bulkhead and the Jastram main processor or DSC 100 box was located in the crew double bunk room just above the lower bunk at the foot and needs suction cups to remove the wall panel for access. The Jastram guys did not know why the interface was ever installed and its not one of their parts. We had a couple of failures of the system until we did the bypass and have had none since.