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 530i Blower Final Stage Fan Resistor May Fail
BMW 530i Problem
Average Mileage: 94,812 mi (35,000 mi - 164,500 mi)
Visitor, 2003 BMW 530i, 60,000 mi
No cool air coming out of vents but you can hear the ac compressor on.
Visitor, 2002 BMW 530i
BLOWER RUNS WHEN CAR IS TURN OFF
Visitor, 2002 BMW 530i, 42,000 mi
FAN BLOWER WILL NOT COME ON
Visitor, 2003 BMW 530i, 113,000 mi
Blower runs when car is off.
Blower turns on and stays on even when vehicle is switched off. The climate control is also unresponsive.
Visitor, 2002 BMW 530i, 119,395 mi
The Blower final stage fan resistor switch failed...result, fan blower will continue to run and drain the battery after a couple of hours after being parked. Listen for sporadic fan blower cycling well after the engine has been cut off. In addition, note air flow exiting the arm rest center console between seat. The air flow pressure will fluctuate in strength, but is noticeably obvious as a function that should normally be switched off. New fan blower switch repair will easily run you over $450.00. Be careful not to get caught up with having to replace the entire blower...not necessary.
Visitor, 2002 BMW 530i, 70,000 mi
fan went on during the night while parked. Battery died. Called road service and replaced the battery. One week later new battery died. Took to dealer, replaced with BMW recommended battery. Died one week later. Took to local shop and paid $100.00 to study problem could not find problem. After a few months of this, I walked into the garage at 11PM one night and heard the heater fan running. Took the car to the dealer the next day, explained what I heard, and they replace some part and the problem is now history. The part was activating the blower to run during the nights which over time drained the battery.
My current problem at 170,000 miles is Air Bag is making a knocking noise and cannot find anything in the internet regarding others having this problem.
Visitor, 2002 BMW 530i, 35,000 mi
But problem started long before, I just had no idea until I searched the net.
Visitor, 2001 BMW 530i, 164,500 mi
The blower will not turn off or cool the car
Visitor, 2002 BMW 530i, 113,000 mi
Replaced fan assembly.