What was found
SMOKE DET SYS NOT TESTING PROPERLY. FOUND NR 3 SDU AT FAULT, NEW SDU INSTALLED, NO HELP. NR 3 SDU CONNECTOR STOWED SYSTEM OPS CHECK NORMAL. NR 3 SMOKE DETECTOR INOP. PULLED AND STOWED NR 3 SDU CONNECTOR DEFERRED. REMOVED AND REPLACED NR 3 MAIN DECK SMOKE DETECTOR, OPS CHECKS SERVICEABLE. T/S WIRING AND FOUND WIRES C AND D SHORTED TOGETHER BETWEEN SMOKE DET AND COCKPIT. REPAIRED WIRE W242B24 AT POS 3 AND 6 AND WIRE W143C24 AT POS 3. SYS CK OK IAW 26-10-5.