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DIY Final Stage / Heater Blower Resistor Change

impee's DIY Final Stage / Heater Blower Resistor change for BMW 318i e46
How to change the Final Stage / Heater Blower Resistor yourself!

Difficulty Level: Medium / Hard

Approximate Time For This Project: 60 mins

Prices: Professional labour costs for FSR change - £35 (private) or £155 (BMW) - per hour X 1 hours

Final Stage Resistor / Heater Blower Resistor / Final Stage Unit BEHR
Part # 64116920365
BMW 1 £87
Final Stage Resistor / Heater Blower Resistor / Final Stage Unit Cheaper, but mine only lasted 12 months!!! 1 £34
Socket Wrench + Extension bar     1  
15mm Torx bit     1  
Flat head screw driver     1  
Phillips head screw driver     1  
Torch LED, as you will need to have it turned on for the whole hour or two!   1  

*prices correct at time of publication

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1) Assemble Your Kit + Notes

Below is the total kit I used. As you can see, there aren't many tools required for this job at all, but it still is a real awkward DIY. It took me only 1 hour, but it has taken others up to 4 hours.

The part we are about to change is (Part #3) generally referred to by 3 different names;

  • Heater Blower Resistor
  • Final Stage Resistor (FSR)
  • Final Stage Unit (FSU)
Kit used to remove FSR


2) Trim Panel - Removal

The FSR will be accessible form the drivers side (on Right Hand Drive cars).

First remove the 2 screws on the small glove compartment and pull the whole of it out.

Next pull out the ping of the expaning rivet and put the rivet out, then screw off with your hand the big round rubber buffer from under the pedals.

Next remove the the 3 remaining visible screws and pull the big trim panel down/out, once you have done this, disconnect the 4 wires:

  • Pull out the 2 wires going to the green Warning Buzzer
  • Pull out the connector going to the long black box
  • Slide the grey plastic clip forward and pop out the black OBD port from the other side of the panel

Plastic Panel

Paenl Removed


3Stepper Motor - Removal

Use a 15mm Torx bit and remove this easily accessible screw.

Next search for the 2nd screw, it will be on the opposite side and hidden quite far behind. This one screw took me 45mins to remove, but I think I was lucky. The method I used was putting only the torx bit and the extension bar on the screw (as the Socket Wench would not fit in together). Next I pushed in the Socket Wrench and attached it to the extension bar and removed the screw very slowly, without anything slipping out of place.

Once you have removed the screw, with the thin flat head screw driver, push the clip back and pull/push the stepper motor to one side.



4) Final Stage / Heater Blower Resistor - Extraction

With the motor out of the way, you will see right behind it a big bunch of wires going into a onnector, pull this out.

You will notice 2 holes for screws, but my car did not have any and if you don't either, then count yourself lucky as you don't have to remove them.

Now push the identified clip back and simply pull the Final Stage / Heater Blower Resistor out and replace it with the new one, ensuring you push the clip back into place.

At this point you can plug the connector back in and start the car to test the new Final Stage / Heater Blower Resistor. If the air flow is ok, then proceed to the next step.


5) Re-assembly

The 2 Final Stage / Heater Blower Resistors look very different, but neved mind as the designs have progressed. They both fit in the same hole correctly.

Fit everything back in the same order. Unfortunately the troublesome screw will take up to 15mins to fit back!

Note: it may be a good idea to only hand tighten the 2 motor screws, so next time you don't need to use a socket wrench to remove them.

old and new comparison of FSRs

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DIY BMW e46 Final Stage / Heater Blower Resistor change by - impee

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