What was found
MAIN CABIN DOOR WILL NOT OPEN. HANDLE POPS OPEN HALF INCH AND ROTATES RIGHT A HALF INCH AND LOCKS UP. UNABLE TO MOVE THE HANDLE. ARRIVED TO ACFT. INSPECTED OUTER HANDLE, AND IT WAS DETERMINED THAT THE SECURITY SEAL, WHEN INSTALLED ON THE HANDLE RATHER THAN ON THE DOOR SEAM, IS CAUSING THE HANDLE TO POP OUTWARD OPPOSITE OF ITS INTENDED OPERATION, RESULTING IN A POTENTIAL JAM. WHEN THE SECURITY SEAL IS NOT INSTALLED ON THE HANDLE, THE DOOR HANDLE OPERATES NORMALLY. HAD AC TOWED INTO THE HANGAR. AS A PRECAUTION, GAINED ACCESS TO THE CABIN DOOR OUTER HANDLE. VERIFIED PROPER RIGGING OF CABIN DOOR. ACCOMPLISHED LATCH MECHANISM PUSH ROD BEARING LUBRICATION OF THE OUTER HANDLE AS REQUIRED. CLOSED ACCESS. PERFORMED OPS CHECK. OPS CHECK SATISFACTORY. ALL WORK DONE IAW AMM 12-20-04.