What was found
RECEIVED AN EXCHANGE FLIGHT DIRECTOR COMPUTER THAT WAS IN AN "INSPECTED" CONDITION ON AN 8130-3 TAG. THE PREVIOUS DISCREPANCY ON THE UNIT THAT WE RECEIVED WAS THAT THE " FLIGHT DIRECTOR COMPUTER IN GLIDE SCOPE MODE IS ALWAYS BELOW THE GLIDESLOPE POINTER. INSTALLED THE UNIT AND NOTICED THAT WE COULD DUPLICATE THE ORIGINAL DISCREPANCY. WHEN THE NR 1 FLIGHT DIRECTOR WAS COUPLED TO THE AUTOPILOT COMPUTER, THE FLIGHT DIRECTOR WOULD FLY AN IMPROPER GLIDESLOPE ANGLE. SWAPPED FLIGHT DIRECTOR COMPUTERS AND FOUND THAT THE PROBLEM FOLLOWED TO THE NR 2 SIDE AND CAUSED THE SAME PROBLEM O THE COPILOTS SIDE. THIS UNIT MUST NOT BE RETURNED TO SERVICE UNTIL THE PROBLEM IS FOUND AND RESOLVED.