Final Stage Unit / Blower Resistor, Aftermarket - E46, E39, X3, X5

Blower fan problems in your BMW E46, E39, X3, and X5 are likely caused by a faulty blower motor resistor, also known as a blower regulator, final stage resistor (FSR) or final stage unit (FSU). It regulates the fan speed coming from the blower motor. If your blower motor seems to have a mind of its own the blower resistor is the first part to check or replace. A failed FSU will cause the fan to not work at all, only work on one speed, or alternate the fan speed on its own. It may even cause battery drain as the blower runs even with the car turned off. Since the FSU is tricky to access, most people simply replace it rather than test it. The majority of FSU failures are caused by old age and excessive heat and a fresh FSU should remedy your problems. However, note that the FSU may be the victim from a related component failing elsewhere in the system. Inspect the plug housing and pins on the wiring harness for signs of excessive heat. When replacing your FSU, also consider changing the microfilter and inspecting the blower motor operation (a failing blower motor may be a contributor to premature FSU failure).

This is a blower motor resistor made by aftermarket supplier URO.

BMW Fitments:

3 Series
E46 (99-05) > 320i
E46 (99-05) > 323Ci
E46 (99-05) > 323i
E46 (99-05) > 325Ci
E46 (99-05) > 325i
E46 (99-05) > 325xi
E46 (99-05) > 328Ci
E46 (99-05) > 328i
E46 (99-05) > 330Ci
E46 (99-05) > 330i
E46 (99-05) > 330xi
5 Series
E39 (96-03) > 525i
E39 (96-03) > 528i
E39 (96-03) > 530i
E39 (96-03) > 540i
E39 (96-03) > M5 (00-03)
X Series
E53 (00-06) > X5 3.0i M54
E53 (00-06) > X5 4.4i M62 4.4L (99-03)
E53 (00-06) > X5 4.4i N62
E53 (00-06) > X5 4.6is M62
E53 (00-06) > X5 4.8is N62
X Series
E83 X3 (04-10) > X3 2.5i
E83 X3 (04-10) > X3 3.0i