Final Stage Resistor fix DIY
 

If you find that your blower motor is pulsing or randomly coming on after your vehicle is turned off, this may be your answer. If your blower motor is on full all the time, this fix may not work as the semiconductors may be shorted at this point. Remove the FSR from your vehicle. Carefully remove the potting material in the corner shown. Go slowly because you don't want to damage the circuit board below. The potting material is soft so this process is relatively easy. You will see two sets of three legs when you have successfully removed this material. To see the board and these pins easier, you may want to put some contact cleaner on the end of a Q-Tip and wipe the board to remove access "small bits" of loose potting material. In most cases, the solder will be broken around these pins connecting to the circuit board causing irratic operation, "blower motor doing it's own thing." Carefully resolder these pins. Make sure you don't bridge any pins with solder. If you do bridge the pins, remove the access solder and try again. Run a small jewelers screw driver between the pins to make sure there are no solder bridges. Once this is done, you are ready to try it. You can see my FSR below. This is what I have done and it now works great. You will see some larger solder connections, I have done this to prevent future problems.
"IF YOU DO THIS PROCESS, YOU ARE DOING IT AT YOUR OWN RISK."
IF YOU DO NOT FEEL CONFIDENT DOING THIS PROCESS, "DON'T DO IT!"

http://a.imageshack.us/img690/5203/bmwfsr0003.jpg
Uploaded with ImageShack.us

Good tip, and it should get most of these FSR's back working. The only issue I see is that it can't fix the original cause if the issue which is the inefficient heat sink spikes which let too much heat build up in the unit. The new FSR units are an updated design with more efficient heat sinks to prevent the solder joints from getting heat damaged.

I agree added sink surface would help. Some larger semiconductors would really help, but the issue is the solder pads. These pads are to small. In the original soldering of the unit, all three pads are the same size as the center pad in each set of three. They were nice enough to leave some extra trace (denoted by solder dots) for the outer pins.

Excellent tip. I have an old FSR in my garage I swapped out that I can try this on. Did you reseal it after the repair?

I did not re-seal my FSR. I figure, if anymore problems develop down the road, I won't have to remove the potting compound a second time. I think this is the last time I will have to touch it though. It works like a brand new unit. (has been for some time.)

Cool DIY. Our FSR has been pulsing for a while but it hasn't gone crazy and have the blower motor come on all the time. Also a great chance to brush up on my solder skills!

This has to be one of the best tips I've seen here. Thanks Heising! My fan quit today so I pulled that bastard out, re-flowed the solder joints and its working again.

Not so easy on a RHD car. Pedals are in the way. I've managed to extract the plug from the FSU but cannot see enough to see what is holding the FSU in place. Any clues please or a photograph of the tab etc that must be holding it. By the way the FSU costs about $400 in the UK.

£400 :wow::wow: I'ts an fsr and it costs about £45.Looky here.... Final Stage Resistor : C3BMW Ltd

edit: By chance I came across this thread, I believe every E53 owner should know about this!

Thank you HEISING!!!!:thumbup:

This worked for me and my fan is blowing again...

symptoms: Front vents quit blowing air... everything else seemed to be in order. I could hear the ac trying to work if I hit the "MAX AC" button but no air flow. If I tried turning on the fan, absolutely nothing happened. Rear vents worked BTW.

This is worth a try for anybody that needs to replace the FSR.
I happen to have a soldering iron and have almost no experience with it. (I use it as a wood burning tool) I have never soldered on a circuit-board before.
The hard/tedious part was removing the potting material and not knowing how deep to dig without scratching the green board.
I used a precision flathead screwdriver to remove the bulk and shaved down a popsicle stick to the size of the flathead to safely remove the remainder. Q-tip dipped in alcohol to clean and better expose the pins and circuit board.


It is mentioned in the how-to, but I'll say it again... You don't need to remove the Glove-box to access the FSR. Just the carpeted part where the outlet is attached and the black plastic piece under the glove box where the foot-well light is attached.

Thank you, thank you, thank you!!:D:D:D:D:D:D:D:D

I just replaced mine last week for $55 plus 1 1/2 hours of beer drinking work. I would recommend just replacing the unit if you have the money. Getting access to this resistor isn't the easiest thing to do so I wouldn't want to have to go in there again...

I just noticed my rear vents not working. I thought I noticed it getting weaker, but could have been in my head. Does this part control the rear fan motor?

Thanks!

This fsr does not effect your rear fan.

Hey guys, glad to see people benefitting from the the DIY! Such an easy fix too. Eventually your new fsr will do the same thing "greggw2gs" so better stock up on the beer :D Hope you saved the old one so you have something to swap in.

Wow I hope the new one lasts long enough to make it worthwhile... I did save the old one but I can't see myself putting that old one back in...

You would not swap in the old one after you have rebuilt it? I guess if your unsure of the process, or don't have a soldering iron, this could pose a problem.

For some, it's better to just purchase a new one.

Repaired doesn't last forever I guess. Mine crapped out again today after less than one year. Time to go with the new design.

Sorry to hear your didn't last. Mine...it has been 2 years and still no problems. Do you think it may be your soldering job? Your solder should look like mine.

Compare photos on page 1.

There is no other part in the FSR that fails other than solder and the motor drivers. Usually the only reason the motor drivers fail is due to the solder, so it's kind of a circle. The biggest problem here is the pad area around the driver is not big enough. This is why the solder area is larger in my rebuilt FSR.
If you can not make the solder job look like my picture, the FSR may not last. The connections get very hot (driver transistors) so its imperative the solder flows properly.

What ever your solution, I wish you luck :thumbup:

Fixed mine today. Yes, solder on second picture looks like why it failed again.. If one can solder I don't see point in buying new one.

Thanks!

I can solder just fine, but I was not able to get the area clean enough so I just went with it. I was surprised it worked at at the time because of the amount of resin garbage left there. Regardless, I was able to get a new part for $35 so no big deal.

Brake clean and some q-tips worked very good for me

Just an update, FSR is still working great.

Its been a year and still works like new!!!

FSR fixed. Thanks Heising
 

Thanks Heising, Your DIY worked like a charm and the FSR is working again (2002 4.4 X5). Its one part that had a slow death. Didnt realise that my Fan could work this fast.:thumbup:

Just did mine last week. It was only a corroded Connector. Quick clean up and it now works great!

Thanks Heising! Air Conditioner blower fan fixed! X5 E53
 

Yesterday I called the dealer and asked how much the factory Final Stage Unit was for my 2003 X5, and they said $144.

At that price, I figured, what have I got to loose in attempting repair of my FSU like you described?

A little digging of the potting material, some soldering and an hour and a half later my AC - heater fan is working great again :thumbup:! Thanks, Heising, for the fix and the pics, they really helped make it easy! $0.00 is real nice!

I posted this just to let googlers know that this fix is current and for real. Pay the .25 cents to get on board at Xoutpost here and get in on the action!

Fish ON!!
-----------<')))><

When I bought my used X from Sanford Acura in Florida a few yrs ago, it had the intermittent fan issue, told them the fan replacement job was a huge job that costs almost $1000 at a BMW dealer (knew it was FSR), they came down $1800 on asking price. It was the FSR, cash in pocket.

It PAYS to read these forums!
 

Smart move TiAGx5! I'll keep that in mind as I shop for my next Bimmer! Looking for an older used 330i with sport pkg and manual transmission. May be a fun daily driver with not quite as bad a gas mileage as my X5!

I'd like to chime in that this free fix only worked for 2 years. I posted back in 2010 that it fixed my intermittent fan speed oscillation. Then, in late 2012, the FSR completely went out and there was no fan at all. Still a great fix, and if the new FSR has the same symptoms, I'll be soldering that one too.

Hi guys. Glad you all are benefiting from this easy fix! :thumbup: The longevity of the fix will depend a lot on the re-soldering quality. The semiconductors get really hot, and the legs will re-open again if not soldered carefully. One good solution to add life to any FSR is to have the blower running "halfway up" or more. The FSR block is cooled by air running over it, when your climate control fan speed is slow, the FSR block will tend to get hot.
If you want to use a solder with a higher melting point (Silver Solder) that's OK too. Lead free has a higher melting point also, but a little tougher to flow.

I wish I knew about this thread earlier. Well, it's bookmarked now.

awesome post - I now have this issue. I will try at it later today

And here is a DIY of how to remove it (just so we have it all in one place)

My blower went dead in the morning and suddenly worked flawlessly towards the afternoon. Ordinarily I would let it be for a while but with the heat I had to get a move on

so I got around to removing the FSU. 3 minutes to remove the panel and get to it and another 15minutes trying to remove the socket. and after about 30 minutes carefully removing the insulation I get around to solder it. its not my best work, but it will have to do

http://i957.photobucket.com/albums/a...psd44dce8b.jpg
http://i957.photobucket.com/albums/a...ps8e26c66b.jpg


so after plugging it back in of course it worked. but now as I write this I just realized I didnt put any form of silicon or gasket maker in to cavity. Is this a necessary step or can it be left as is? I did cover it with electrical tape but I didnt give it much thought till now

Hello Z168. Glad to hear it worked. The soldering needs to be cleaned up and flowed properly though, or you may find it will fail soon again. Sometimes scraping the existing copper traces helps the new solder to flow easier. I see the center pins have almost no solder on them. Make sure the pads are cleaned and flow solder to them. Liquid Rosin Flux really helps this process. These units get so hot, any soldering errors will quickly show in premature failure.

I didn't seal my unit back up. I just left it open. This is up to you to decide.

Good Luck!:thumbup:

My soldering gun gets a little too hot for comfort so I had to be quick. Im afraid I might fry the circuit board. I should probably get a small iron instead

Thanks again Heising!

Well, it's been about a year, and mine has quit again. The last time, it was just a little corrosion on the plug that connects to the FSR. I have to pull it out when I get home tonight and see if I have the same problem again, or if I have to get out the soldering iron.

Mine hasnt failed but it might be a good idea to buy a replacement for it just in case this happens again this summer

Well, I took it out last night. I tried to remove the potting material, so I could re solder the connections, but the potting was so hard that I was afraid of damaging the unit in trying to remove it. After about an hour of scraping, chipping, cutting, etc, I finally gave up. I put the unit back in the car and planned on buying a new one today. When I started the car to move it after I had finished - it was working again! So far today it hasn't failed yet. I guess I'll just wait until it dies again, and then buy a new one. Are these available at auto parts stores, or are they dealer only?

Hi ChevDog1. Your unit will run like new again if you can get to the solder joints and re-solder them. Just unplugging, and re plugging the FSR back in again will create enough movement to make the bad solder touch the trace, giving you the false hope that the problem is cured. If you are good at soldering, you should get years of life yet. My unit is still running.

Good Luck :thumbup:

I can solder just fine. What I had trouble with is getting all of that crap off that they sealed the unit with. It's so old and hard that I'm afraid I'll damage the unit trying to remove it.

If your thinking of buying a new one, what have you got to loose?

Pardon my ignorance but where exactly is this FSR located?

In my X5, it's located in the passenger footwell, above the tranny tunnel, against the firewall.

Thanks for replying!

Blower dead. Replaced FSU and still dead. Finally reached the blower wheel/blades with a stick and freed the seized wheel/blades and blower came back the life. The wheel is located inside the housing of the FSU.

2003 X5 Blower was pulsing on/off after ignition key was turned off. Dealer wanted $190 before tax for a new FSR. I followed your instructions and after a total repair time of about 2 hours, it appears to work fine. Removing the potting compound was a challenge, but it comes off with care and patience.

Thanks for a well documented DIY fixit.

Do you (or another member) have a link for the updated FSR unit, with the updated and improved design?

I think I'll order an updated unit, and just swap my proactively...



--Scott

Save some money and order from Rockauto.com
its called a Blower Motor Control Module/Resistor in their catalogue and there are many prices/brands. I bought the Valeo myself last year (though it was only $60 I believe then).

But the Hella brand sells for just $37. So thats nice and cheap

Noted, and thanks for the info and advice! I believe I'll shelf the info, and pursue a repair if mine faults in the future. I'm sure the newer replacement units are all the updated (improved) heat-sink design anyway.



--Scott