E46 aircond blower problem.

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Hi guys, i just bought a 3series E46 unreg 2001 model a few weeks ago, a few days after handover, i took the car long distance kl-manjung, i found out that my aircond on 'auto' mode will not function (blower running but hot air coming out. I also found out that the compressor was heavily iced up) on long distance doing 120++km/h but in town driving no problem. So i took it back to the dealer and change the aircond sensor with new BMW parts (mech tested found sensor faulty). Now the problem seems to reoccur ; aircond setpoint @ 19-22deg the blower indicate almost full blast but the air coming out is slow. i haven't test on long distance travel yet. But a few days ago from KLIA to ampang aircond set@19deg 'Auto' mode, the blower was blowing slowly but indication full. Can anyone tell me, is this normal?? or is there something wrong?? as i have never used a BMW b4 this. Does anyone had this problem b4?? thanx.