3502 Air dryer Fault. To check & rectify ~~~~~ 3502 Air dryer Fault. (DT Check)  3502 found FC 704 (Air Dryer Fault). Replaced air dryer. Security/function check - OK. Monitor air dryer operation able to purge at 2 min interval. No air leak & no air dryer fault indication. Air leak test (0.4 bar/5 min) - OK.  Redzwan/Koon PL 44549 #3502 Air Dryer S/N : OLD : 3515060261 NEW : 3515289113