What was found
THE GARMIN GPS-155 INSTALLATION DOCUMENT DOES NOT ALERT THE INSTALLING AGENCY OF THE POSSIBILITY THAT THE NAV 1 SYSTEM WILL DISPLAY ERRONEOUS INFORMATION WHEN THE GPS-155 IS INSTALLED IAW GARMIN DOCUMENT 190-00065-02, REV G, 9-13-94. THIS SITUATION WILL OCCUR WHEN PILOT SELECTS 'GPS' MODE, & THE OBS INPUTS TO THE NAV 1 RECEIVER ARE LEFT OPEN-CIRCUITED. ON FIGURES 1-3, PAGE 24 (GARMIN GPS-155 INSTALL), THE NAV 1 SOURCE ON THE SCHEMATIC IS NOT DEFINDED TO A SPECIFIC MODEL OF NAV RECEIVER. THERE ARE SEVERAL NAV SYSTEM (I.E., KING KNS-80, KNS-81, ETC.) THAT WILL NOT OPERATE CORRECTLY WITH THE OBS LINES OPEN-CIRCUITED.