How Does A Final Stage Resistor Work

July 08, 2017

It usually shows up as the fan blowing at a faster speed then it is set to. Lathejockey81 jun 14 15 at 1510.

Bmw E46 330 325 Final Stage Resistor Blower Motor Removal

Blower Motor Resistor How It Works Symptoms Problems

How Electronic Components Work

The blower final stage fan resistor is known to fail.

How does a final stage resistor work. It receives the driver demand signal from the hvac control panel and sends a high current signal to control blower motor speed. 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. Sometimes a blower motor resistor might fail due to problems with the blower motor itself.

A common symptom of a failing final stage unit is the blower motor not operating in accordance to how the controls are set as if the blower had a mind of its own. The blower motor resistor or final stage varies voltage to the blower motor to achieve the desired airflow speed. Bmw e39 fsu unit replacement tutorial in this video i show you how to replace repair the bmw 5 series heater blower fan resistor or as bmw call it final stage unit fsu.

A resistor works by converting electrical energy into heat which is dissipated into the air. Final stage resistors are resistors just like any other and will suffer the same failure modes. Parts needed final stage unit part 64116920365 check bmw for latest part tools needed t 20 socket philips screw driver.

In our case the ohmmeter shows open circuit which means the resistor has failed. A failing final stage resistor will cause the cabin fan to blow at sporadic speeds. 2 faulty final stage resistor unit the final stage unit blower resistor may have failed.

The ee stack exchange might also be a great place for this question. This means after replacing the blower motor resistor check if the blower motor runs freely and doesnt make any noise.