Max a/c button doesn't turn blow fan at high speed

[mmunro]

Max a/c button does not turn blowers to highspeed. Occasionally/intermittently, but not always, when left in max, the blower does jump to high speed after 5 or 10 mins.
Also manually turning fan speed up to full, doesn't cause blowers to go to high speed.
Any ideas ?

[BM-Beast]

Sounds like the car's computer might be detecting the beginning of a low battery situation & when the car has run long enuf to recgarge the batt. a bit the fan kicks back up.

[GeezTech]

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[mmunro]

Just installing a new battery isn't enough. A dealer needs to "register it" to the computer system. When an old battery is detected low-voltage, the computer system sets some of the "electrical load consumer priorities" to 0, hence not allowing them to run. Max A/C is one of these. The intent of this is to protect the remaining battery voltage, so that the driver isn't stranded by being unable to start the car. These 0 settings are only reset by the "register battery process". btw .. even though the dealer recommends the BMW battery .. a new after market battery does work fine, but probably won't last as long, due to the high draw for these cars.

[wilsonho]

My car had the same max a/c problem. It also had the low battery warning message when the radio is on while it is parked with engine off. I just had the battery replaced and fixed both problems. This is what I have on my service order. I was wondering if the registration is really needed. If it is, that means only dealer can replace the battery which is very bad in my opinion.

DL001 MISC. ELECTRICAL REPAIRS
465 CP $140
1 61-21-6-091-815 BATTERY FROM EXIDE
( WARRANTY : 612010 $246.4

39531 REPLACED VEHICLE BATTERY WEAK. REGISTERED BATTERY TO VEHICLE WITH CT1C UNIT.


I do have a new problem after the new battery installed and I hope someone can shed some light into the problem. I start getting crackling noise coming out from the speakers whether I am listening to radio of CD. It is not coming from one particular speaker but randomly on all speakers. It is kind of annoying when listening to music. I am not sure what they did that could caused this problem when changing out the battery.

Thanks

03’ 745i