TC reported Smoke External at Front M1 car. Rear Train T433 line clear and reported no abnormality. Staff(AMK) checked and confirmed no sign of heat/smoke or fi re. No abnormalities. ~~~~~ TC reported Smoke External at Front M1(1634) car. Rear Train T433 line clear and reported no abnormality.    Staff(AMK) checked and confirmed no sign of heat/smoke or fire. No abnormalities.  1634 FC 721 (Smoke External). Checked firewire cable at battery & underframe, found no burning marks/smell. Swapped #1634 FRPR panel (S/N 316) to #2634 (S/N 319). Monitor & fault still occurred. OPS 20 raised to replace smoke detector at RSDBSD.  Shafie/Kamarul 44621 To replace smoke detector     Check the above mention FC-721.Replaced the external smoke detector due to water in it.Security check and tested ok-fault clear. Done by Saini/Haslan. 1/03/22