What was found
AFTER TAKEOFF GEAR WOULD NOT RETRACT. TROUBLESHOT SYSTEM AND FOUND LANDING GEAR CONTROL UNIT NOT FUNCTIONING PROPERLY. REMOVED CONTROL UNIT S/N - 0110 AND INSTALLED CONTROL UNIT S/N - 0088. PERFORMED OPERATIONAL CHECK, NO DEFECTS NOTED AT THIS TIME IAW CE560XL AMM 32-30-01, 32-01-00.