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Embarked upon this project today, spent 45 mins getting the FSR out of the donor car, and then when I got back to my ride, I plugged the battery cables back in to test the radio I had just installed. I turned the key on and the fan runs fine now. Guess I have a spare now.

Also tried the instructions to program a key remote, and didn't read until the end that you needed a working key. I did not. Worked anyway.
BMW redesigned the FSR at some point, the newer design doesn't look the same. It's significantly different. Hopefully the donor you pulled was the newer replacement part.

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2000 323i Touring Auto 130K miles

Finally my FSR died. I got new one $50 from BMA Parts, Berh Made in China, not Germany. They warranted 1 year so I will see how the Chinese part works.

I removed the two fuses related to AC circuit but didn't remove battery. Removed the glove box without touching those hangers with the rivets.
Removed two T20 screws holding the flapper motor (to gain access to the FSR) and just pushed it away for access to the FSR screws. Trick: placed rag or tissue paper to seal off places that you don't want the T20 screws to fall in. After unthreaded the screw, pull the tool out and then place a magnet on a small screwdriver as a tool to retrieve the screw -- this way it won't fall off into the black hole. For installation, I use the same torx driver (without magnet) with the screw on its tip, carefully on a horizontal line up the screw hole and done. Removed the FSR with its plug, then unplugged the connector. Install: install the FSR without connector, then plug the connector.

People call the thing Final Stage Resistor but the device is not a resistor pot as used in the older BMW. This is a transistor linear power amplifier (as linear audio amplifier with massive heat), or motor driver, takes in an analog control voltage and output a high current analog voltage to control the fan speed, hence it dissipate a lot of heat and so the massive heatsink. Many people believe the very hot FSR was the reason for its failure, and had asked the question why BMW didn't design this motor driver using PWM (low heat loss) instead of linear amplifier? Bmw did use PWM for the radiator and AC fan, so why not for the cabin fan? I believe someone did make a PWM FSR after-maket part before but no longer active. I was interested on this question myself and studied the system during this work. It is fairly easy for me to design a 60A PWM motor driver in the space of the FSR body, and it will run cool like a cucumber. My thought was that due to the sensitive digital control/communication buses in the big wire bundle near FSR location (the FSR's harness was bundled together with many other wires), BMW didn't want to take the chances of electromagnet noise generated by the fast switching PWM high current FSR that could cause error in the air-bag system, CAN bus and other buses. Therefore they choose to use the more quiet linear power amplifier FSR. I also think the new updated design FSR is much better compare to the original unit. If one want to use a PWM FSR, one should carefully shield all PWM high current signals from other sensitive wires and buses.
 

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2002 330ci - 30k miles.

Great DIY and the many follow-up posts add much value.

Ordered my FSR from Amazon (made by Valeo and sold through BMAparts.com) for $48.

Symptoms limited to blower "huffing" for the first 30 seconds following a cold start. This thread convinced me to make the repair before conditions became worse.

Will echo comments about using magnetized torx/phillips drivers. No torx on my FSR, but 2 T-20s holding the module in front of FSR, and as the only owner of this car, I am certain it came from the factory without screws in the FSR. The top left module T-20 is a little difficult to see, and this is where magnetized drivers might save you from losing a screw. FSR unclipped easily, thanks to knowing to push the single clip toward front of car. My only hiccup was that when replacing the two T-20s I mistakenly threaded the bottom right one into the FSR housing rather than the module -- it fits perfectly, but whereas the FSR is firmly secured by its clip, the module needs both T-20s to be properly secured. Caught and fixed my mistake. Replacing the trim plate also took a little patience as a little flexing of it is necessary to get it back in place and there is a tab and a clip that require exact placement. Total repair time of about an hour.

No more huffing. Thank you all.
 

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Just changed mine along with the fuel pump relay! Was probably the smoothest DIY yet, as I didn't hit any unforeseen roadblocks (that seem to always pop up).

Great instructions. Thanks a lot for this.

PRO TIP: Use your phone camera and turn the flash on! I did this with my iphone and viewed the video as I shined the light back where the FSU was. I didn't ever have to put my head back there, I just used my phone to guide the screwdriver.
 

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well, my FSR failed on Friday, it had previously did the huf huff huff symptoms and then would occasionally just stop blowing, usually turning the fan control to off for a minute of two would let it come back on again......then for the last year its been fine, but on Friday after work, it decided it was going to blow no more, after I got home and went back out it came on for a few seconds then died again and this morning going to work, nada...so I have ordered the BEHR replacement from FCP EURO and while I am waiting I went out to the parking lot and removed my glovebox and lower tray.......I hope this goes well........
 

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My FSR didn't have any screws holding it in. It has previously been replaced at the dealer... should I get screws for this? The pelican part DIY for example only mentions one screw for the FSR.

Here you can see the lower right screw (left one goes to the module in front of the FSR which i had removed)



Here you can see both holes and notice how the FSR one appears to have never had a screw in it at all....



I don't have a good picture for the top FSR hole however it appeared to have the same unmolested screw hole. Should I hit up a junkyard car to find these screws or are they not important?
 

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Just did my FSR. I had 2 torx bolts on my original BMW Valeo unit. 1 note, I dealt with the sporadic fan speed for about 4 years up until 3 months ago when the fan would come on with the climate control being off or when the car was completely off(key out). The fan would come on go off intermittently while the car was parked. This would lead to a dead battery after not driving for a day. Being a 40 amp fuse module I can see that this unit was the culprit for the parastic battery drain. New FSR, no dead battery!
 

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For what it's worth, I'm the original owner of a 2003 325i M56. The FSR didn't have the 2 torx screws holding it in. It looks to be the original FSR and it should be to my knowledge.

In addition the swap is not that bad at all; perhaps there are small differences between models. You do need a screwdriver length or longer T20 to get at it easily.
 

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When I pulled the FSU (thanks to this awesome DIY), I found that the FSU shorted internally and melted the plug and shorted pins attached to it.. I know from previous accounts that it could cause a potential fire under the dash and I found it just in time.. Also, I replaced everything with OEM parts including the plug and pins, which I was surprised the dealer even had.... AC back up and all is well.... ;)
 

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Do I need to read all 13 pages or can someone help me out? AC stopped blowing for 2 days and is working again now. My assumption is it will go sometime soon.
 

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Do I need to read all 13 pages or can someone help me out? AC stopped blowing for 2 days and is working again now. My assumption is it will go sometime soon.
If it's original, as far as you know, I would at least pull it out and see if it's the newer design. Post 253 explains why. Change it if it's the older one.
It's not a technically challenging job, just a PITA.

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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.

BMW E46 DIY Final Stage Unit - Resistor

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

I wish the pictures were still available!
 
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