TIMS showed Smoke External Alarm at car1532. Staff(KTB) checked and confirmed no signs of smoke / f ire / burning smell on exterior or interior of train. Rear T 254 line clear and confirmed no abnormalities. TIMS showed S ~~~~~ 1532 TIMS showed Smoke External Alarm. Staff(KTB) checked and confirmed no signs of smoke/fire/burning smell on exterior or interior of train. Rear T254 line clear and confirmed no abnormalities.  1532 FC : 721 smoke external. Swapped SDR11 from #1532 to #2532 for monitoring. OPS 20 raised to check smoke external detector.  Shaun Lau 45315 BSD: 1532 - To check External smoke detector.  1532 check and found smoke external detector water ingress, replaced smoke detector and function check ok. S/No: N/A Notification: 2564649 Done by: Yusof & Haziq. 25/01/24.