#3670 B side underframe hising sound and ~~~~~ DT check found #3670 B side underframe hising sound To rectify.  Check and found 3670 air dryer exhaust port non-stop purging and cause MR unable to charge up. Further check dryer wire connection ok. Voltage output supply ok. Air dryer change out done. Function test ok. Air compressor charging time 2min20sec. Cut in:8.7bar and Cut out 10.25bar. Air leak test 0.4bar/5min. 3670 old:015-12586 new:3515370302 notif rsw:21319855 Done by: Koh/ Jack 44473