The blower final stage fan resistor is known to fail. Symptoms are the heater fan speed varies regardless of the setting, the fan will not turn off when the car is switched off, or the fan will not switch on at all.Google+
Car Problem Reports
BMW 328i Blower Final Stage Fan Resistor May Fail
BMW 328i Problem
Average Mileage: 143,009 mi (65,000 mi - 218,000 mi)
The air conditioner would work, and you could tell it was cold but the air would not blow out of the vents. Also this would happen off and on for about 6 months. The air conditioning would work and blow cold air, then it seemed like on the really HOT days it would not blow the cold air at all, so i had enough!!! Replaced the final stage transistor and Yeah that fixed the problem!!!!!!!!!!!
Visitor, 2000 BMW 328i, 150,000 mi
Fan does not turn of even when I turn the car off. I replaced the FST two weeks ago and it worked perfectly fine then but now it won't turn off. Any other solutions?
Visitor, 1997 BMW 328i, 160,000 mi
A/C starts and stops unpredictably as if a connection is loose.
Perhaps I will have to try replacing the final stage fan transistor whatever that is.
Visitor, 1997 BMW 328i, 90,000 mi
sometimes fan doesnt work
Visitor, 1999 BMW 328i, 102,090 mi
Blower goes on intermittently. They want to replace whole resistor for $400+
Visitor, 1997 BMW 328i, 143,000 mi
the a/c would turn on when it wanted,first i thought it was a loose connection point, wrong! I'm now going to replace the final stage resistor, pray to god. I live in Las Vegas, and it's HOT!!!!!
Visitor, 1999 BMW 328i, 212,000 mi
AC/Heater fan only works sporadically and almost never when you need it. No solution