3504 During DT found Air Dryer fault. ~~~~~ 3504 During DT found Air Dryer fault.  3504 air dryer & micromesh filter replaced. Security check & function test 2 min change-over purging - OK. But air dryer fault still persisted. OPS 20 raised to follow-up. 3504 Air Dryer S/N : OLD : 3512450002    NEW : 3573130028  Aminur/Ridzuwan To continue rectification.  503/504 continuity check on 6614/6622/LGD - OK. Found pressure s/w connector pin #2 dislodged. Replaced connector with available spare. Function check twin dryer change-over, cut-in/out - OK. Further monitor for 2 hrs, no fault occurred.  Kana 44220     Check Twin Airdryer able to change over after compressor cut in/out.N . Checked by Imran. 01/03/21