TIMS showed Smoke External at car 1641.Staff(BBT) checked and confirmed no sign of smoke on exterio r or interior of train. ~~~~~ CE: 1641 smoke external fault unable to reset.     #1641-Found water ingress in smoke detector unit. Change out, normalise breaker and tested ok. Reseal done. Not: 2467703 Raised to CSC. Done by Koh/Rizman. 05/03/23.