TIMS showed Smoke External Alarm at car3676. Staff(YWT) checked and confirmed no signs of smoke on exterior or interior of train. Rear T230 line clear and conf irmed no abnormalities. TIMS showed Smoke External Alarm at ~~~~~ TIMS showed Smoke External Alarm at car     Check and found original have no plaseal,fault due to water ingress.Replaced new smoke detector and function check ok. Check plaseal on all smoke detector. Smoke detector:- Not: 2484837 Done by Asruddin/Haslan.  02/05/23