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Discussion Starter #1 (Edited)
Here's my DIY on replacing the Final Stage Unit (Resistor).

I know there's other DIYs on this, but i tried to create one with better pictures. It can be a little confusing when you're trying to replace the unit.

A failing Final Stage Resistor will cause the cabin fan to blow at sporadic speeds. It usually shows up as the fan blowing at a faster speed then it is set to.

http://www.bokchoys.com/differential/diy_final_stage_unit.htm

Parts Needed:
Final Stage Unit (Part # 64116920365)
(Check BMW for latest part #)

Tools Needed
T-20 Socket
Philips Screw Driver

1. Remove Glove compartment. (6) Philips Screws. Unplug light and flash light wires.



2. Remove the lower tray holding footwell light. Unplug light.



3. The final stage resistor is located behind the footwell air duct as seen in the picture. There's a module blocking it, you'll need to move it out of the way before you can access the Final Stage Resistor. Move this module by removing the (2) T-20 Screws. There's a hose that's connected to this module that you don't need remove. Just let the module dangle.



4. You should be able to see the Final Stage Resistor now. Remove Final Stage Resistor by unscrewing the (2) T-20 screws. Unplug the wire. Un-clip unit and pull out.



5. Reconnect everything in reverse order and you're done.

Picture of a new final stage resistor

 

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Thanks for the contribution! Great pics and details! :thumbup:
 

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You forgot a part: Tiny hands. I just did this yesterday and between wedging my hands into that little space and contorting myself across the doorsill I do not want to do this job again any time soon...
 

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Thanks for posting your DIY! My symptoms were a blower that stopped working altogether for a couple of days, then worked again for a couple, then stopped again. I just did this job this morning, and your photos and descriptions made it much easier to complete. Took me about an hour, and I now have AC blowing once again. :bow:

One suggestion, though. You might want to include some stretching exercises at the beginning for those of us who are less than limber. Might prevent that expensive trip to the chiropractor! ;)
 

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Thanks for putting this together. I did the replacement today and your DIY was a big help in tracking down the location of the FSR.

My symptoms were pretty similar to what others have experienced - erratic fan speed (speeding up and then slowing down rapidly when on "auto") and then ultimately no fan at all regardless of the mode.

After replacing the FSR, everything is working as expected. Thanks again for the DIY.
 

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Good write-up and great pics. Not to criticize other DIY's, but so many have pics from weird, upside down, etc. angles, it's easy to get disoriented.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
 

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Discussion Starter #10
Thanks for the compliments. The first time I did one of these, I started taking apart the wrong part of the car. It probably took me a good 3-4 hours cuz I didn't know where the FSR was located.
 

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My Climate Control seems possessed.. never at the right speed (temperature is fine.) Was going to replace the unit.. but could this be the cause of the sporadic speed??
 

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I remember changing out mine, in the garage at night with hardly any light, what a pain in the butt. Very worth it though... congrats...
 

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Discussion Starter #13
My Climate Control seems possessed.. never at the right speed (temperature is fine.) Was going to replace the unit.. but could this be the cause of the sporadic speed??
yup... when the Final stage resistor fails, the fan will blow at sporadic speeds. Time to replace it.
 

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My FSR also had a second symptom: A high-pitched whining sound every once in a while. I first thought it was a bearing starting to go on my blower motor...
 

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Sometimes-not all when I 1st start the car up the HVAC blower speed goes up & down. But not for the past few months. I'll be replacing the FSR soon.
 

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This was an awesome DIY, thanks man! The Final Stage Resistor was my problem and it's nice to have controlled heat coming into winter here!
 

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great diy! sadly mine had 3 screws for some odd reason and it ended up taking me about 3 hours :(
 
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