Replacing the final stage unit/blower motor resistor (E39)

2001 535i
Thank you so much all of you especially Elvis. I fitted this unit today, nearly pulled my back out through all the twisting, swore a few times, and even worse broke a nail! But managed to do it in 20 minutes, 15 of which were taken up trying to find the little beast. A light strapped to the forehead would have been helpful, but the instructions you gave were perfect.
thank you again, love girlie girl xxx

2003 530i.

just replaced mine. the old part looks just like the old one shown in the first post. it used to be stop and go like it was possessed and now the a/c speed is as consistent as new for a $65 and 20 mins of sweating in the garage.

thank you!

tip for anyone who try to do it in the future.

- be patient.
- getting the connector off took the most time. there are 2 clips on opposing ends, disengage one and then wiggle it out partly and then disengage the other one.
- once the clip is off, push it aside so it won't block the passage off the FSU.
- disengage the FSU clip. wiggle the FSU.
- for me, the FSU comes out half way and got stuck again. i tried pulling from the front but there are no good leverage point. in the end, i managed to reach around to the back (have to move away some insulation foam) and voila it came out.

- putting everything back was simple.

Its took for me 5 min. )))

Thanks for the advice, However i have a 3 series Bmw and it was a little more difficult.
It took about an hour being careful, 3 series owners you can access it by taking the glove box & frame apart appx. 10 screws (15) min. Then i removed the floor vent, Just pull it and it will detach itself (Just remember how it came out) 1 Min, Then unscrew the motor in front of the replacement part (2 screws 3 Min) Then onscrew the replacement part (2 screws 3 Min, pull the placstic support down and pull unit out with wires attached if you want. Then unhook wires and attach to new unit and replace unit, Then replace everything back. (my car has vinyl not carpet so i just bent it a little to replace vent.

Originally Posted by bluebee

For the cross-linked record, JimLev provided a nice adjunct to cn90's previous suggestion on how to test the blower motor versus the FSU in this thread today:
- E39 (1997 - 2003) > Help!!!!!!!!!!!!!!!!!!!!!!!!!!




BTW, notice this statement is relevant to dead batteries:
"You don't need to have the key on to check the blower motor, 12 volts is always at the FSU connector."

Wow! This is just what I was looking for. I replaced my FSU about two and a half years ago and it just went out so I just replaced it again. It worked for a few days in the same manner as the old one and now has completely died out. This will help determine if it is the blower motor or just a bad brand new FSU. Thanks. Will update.

Originally Posted by stevendc

check the basics first: fuses, wiring harnesses', settings on the vents (blue is cold, red is hot) etc..........do you think the instrument console could be bad? I don't think this is related to the FSU at all. Let me check my Haynes Manual..........

FUSES? Where would one find fuses for this system? Better yet, would the fan have the characteristics posted many times on here as having a mind of it's own IF there was a bad fuse or simply NOT WORK AT ALL if the fuse is bad?

Thanks.

I never found the fuse (? # 76 ?) To anyone considering ebay, I would not bother since you can find them from a part supplier at great prices. I ordered an OEM from Autohausaz this month for just under $57 to my door!! including a clutch petal pad and some black clips.

Originally Posted by mi-matt

I never found the fuse (? # 76 ?) To anyone considering ebay, I would not bother since you can find them from a part supplier at great prices. I ordered an OEM from Autohausaz this month for just under $57 to my door!! including a clutch petal pad and some black clips.

$57 for what part?

Thank you so very much for sharing this information. Freaking Awesome!
Being out of work a couple of years I purchased the Peake reader which came up with A8 Thermostat coolant jammed opened. I replaced thermostat...no help outside the education on taking the thing apart. Bimmerfest provides the very best of what the internet provides us today...great information when you get to the right place.

The car is very well thought out and the connectors pretty simple once you know what you are looking for. Thanks to you I know what to look for. Grazie Millie !!

Well, this is my first time to post. Have a 2001 530i with the A/C possesed like described. Bought the part yesterday; put it in today as described. No problem there. However, it didn't fix the problem. What else could be wrong?

It worked!!

i've known about the FSU problem for some time... but it just happened to my 2003 E39 this past Friday. Ordered the part from autohausaz.com this weekend and it arrived today. popped it in under 10 minutes and all is well again! cost was $52.09. thanks for an awesome BMW community that supports each other!

TIP: guys, if you're having a hard time pulling the plug off 'cause it's been there untouched for the last 9 yrs like mine, get yourself some robogrip pliers or something similar. came right off and saved my finger tips and laying in an awkward position for too long. use to do some car/mobile electronic stuff and realized using pliers to remove those plastic wire plugs made life so much better than using fingers and nails.

Hi Elvis530i,

Very nice job documenting and photo graphing the FSU replacement! It was because of your thoroughness, that i built up the courage to try this job myself. I bought the part today and hope to replace it tomorrow. I was so pleased with your documentation, that i registered to bimmerfest, just so i could send you this thank you!

-Bob Pisone
Leesburg, VA

Hi All -

I love this DIY, and I'm not often given to giving up...but, I cannot get that infernal FSU out.

I've got the harness off...I've tried pressing the tab...nothing!

It's 14 degrees in Minnesota right now, the sun is going down...I'm cold. I have a headache. My fingers are throbbing and cut to ribbons. I feel like a failure. I just told the cat to find a new home. I've retreated from life and all responsibilities.

But...I ain't bored.

Also...if it helps...I've got fat hands, and a shoulder that could use a couple of wire ties and some Silly Putty.

It's a 2000 528i...any help, prayer, shaman, medical help, psychological rewiring, morale reconstruction, or coffee cake would be much appreciated.

And...all kidding aside...you guys truly are a remarkable resource and of great assistance.

I am reporting my tips

Originally Posted by EconoBox

Wow, this DIY was a huge headache.
No way this will take anyone 15 mins.
It took me over an hour.

Here are some awesome tips for anyone doing this job:

1) When you're trying to unclip the plug, get it so the clips are unseated and can stay that way b/c you've loosened it slightly.
From there, use a flathead screwdriver to pry it away. This was the only way I got the plug off. WHEW! Otherwise, it's impossible to remove the plug.

2) It was a nightmare trying to pull the FSU out. There is no room for 2 hands, yet you need 3 if you want light!
I was trying to pull it out by grabbing the damn socket thing. I tried to grab that little hole with needlenose pliers. I must have done this for 20 mins.
THEN I finally reached around to the BACK, and PUSHED it out. Holy ****, that made it 100x easier.

3) When trying to install the new FSU, you need to push the harness/wires UP AND OUT of the way.
Yet, there is NO extra room anywhere. (And by now, your neck and arms are starting to tire)
So, use a screwdriver to hold the wires UP over the cavity in order to get the FSU past them.

Lastly, I was never able to fully seat my new FSU. It just would not go all the way in.
There is no way to get it past that release latch again.
I spent 15 mins trying to push it in, and then said F it.
There is no way it can fall out with the jack plugged in.
Did this happen to anyone else?

My FSU wasn't even defective, but for $50 I figured I'd just change it.
But the original FSU in my 2001 530i seemed to have the updated heat sink design. (Same number of prongs)
It did not have the fewer and thicker prongs. So, this DIY was probably totally unnecessary.

Thanks, Eco...

I'm not even sure I'm pressing that tab down...the thing won't budge.

Also...I saw your tips earlier, and tried to follow. What did you mean by pushing it out from behind? I tried that, too...just couldn't figure out how to get my hand behind the FSU, while keeping the tab pressed down.

Thanks again for the response!

I did my 530I this morning when it was 12 degrees out. I had some issues getting the plug off then the new one didn't want to snap in. I will say all in all it wasn't to bad to do it myself thank you for the guide!

I am, like so many here, thankful for the original post and everyone else that weighed in. I am on my 3rd 540i, and this one displayed the classic symptoms, meaning the fan had a mind of its own. But I also had some werid throttle issues that I was thinking meant a replacement throttle or something. FSR change was amazing. Fixed the fan, AND a ton of the throttle issues. This is not an easy fix, if you are tall, but the OP was SO helpful, I persevered and got it done. THANKS to all.

Great post. This is my next project

Great instructions - big help

Thanks,

Just my luck - my battery & alt tested good at both O'Reillys and Autozone today ...
> E39 (1997 - 2003) > It's my turn again: Dead battery ... two days in a row ... (yeah, I know what to do)

Like everyone else, I had replaced my FSU somewhere earlier in this epic thread <=== EDIT: It looks like I first came here in post #138 on 3/26/2008
EDIT: Found the dates:

a) I had put in a new FSU in, oh, about three or four years ago (need to check) <=== here's the thread ... 2/2/2009
b) I had put in a new alternator & belt drive system a few years ago <=== here's the thread 7/26/2010
c) I had put in a new battery only a couple of years ago <=== here's the thread ... 9/19/2011

So now I'm gonna re-read this canonical thread backward, to try to figure out which fuse is the one for the FSU ...

I'll edit this post once I figure out which one it is.

EDIT: OK. I found it. It's Fuse 76. Ensconced deeply under the glovebox (not in the glovebox, where fuses F1 to F46 lie).
Doing my homework, I find these quotes scattered about the forum, which relate to unplugging the FSU fuses:

Originally Posted by pleiades

That's a single, square socket housing for two large fuses, F75 & F76, unlike the individual socket arrangements shown in the attached photos. And yeah .... it's hard to get your hand up in there (be sure to disconnect the battery first), let alone finagle the fuses upward and out with your fingers. Be sure to put the right fuse back into the right slot, too. Easily interchangeable.....

BEHIND GLOVEBOX (look from underneath):
F75 = 50A, Auxiliary fan (some say it's red)
F76 = 40A, Heater blower (some say it's yellow) [cn90 says it should have 12V when HVAC is turned on]

Or, I can just unplug the FSU ...

Originally Posted by JimLev

Pull the bottom plastic panel off that is under the glove box, pull it straight back toward the seat.
Then unhook the side supports for the glove box.
This is what your will see.

Originally Posted by rog5878

To access F75 and F76 ... close the glove box and behind the glove box is a plastic panel with a hole in it (the panel is directly behind the glove box) Pull it towards you. Takes a bit of a nudge.
Then there are all kinds of wires bound together and various connectors that if you pull out will probably incapacitate the car -- who knows. I had to contort myself to lay on my back and look up in the well on the passenger side.
Yes, the two large fuses -- 75 and 76 are in the middle of this mess, and yes, it is a tight fit (took forever to locate them with the little flash light; some say they are obvious but they weren't to me; of course, now I know exactly where to look). God knows how one gets them in. To get the fuses out, I had to nudge the first fuse on each side -- couple of sparks -- God knows what those shorts did -- and finally it came out -- the fan stopped.

Originally Posted by bluebee

1. Car dies periodically (and blower has wierdities at the same time)
2. Unplug FSU ...
3. If intermittent battery death stops, then you've pinpointed the problem
4. Replace FSU

If it's not the FSU, then I'll need to go, one by one, down all 88 fuse slots (F1 to F114).

To measure the current drain from your battery you will need to connect your multi meter in series with the battery and NOT in parallel across the positive and negative terminals. This would be OK to do this if you are measuring voltage. To measure current disconnect the negative terminal (I use the neg but you can use either), set your millimeter to measure amps and connect the meter between the battery terminal and the disconnected cable. If you don't have an amp meter then use a 12V test light bulb. The bulb will have a very low glow due to the current drawl from your clock, computer, etc. If the trunk light is on you will want to pull the bulb or fuse. If it is brighter then a low glow then you have a short somewhere in your car. If you want to see what the difference between a low glow (low amp draw) and a high amp draw turn on your head lights. You can pull each fuse and see if there is a change at the amp meter or pull the fuse and insert the amp meter across the fuse terminals (need to reconnect the battery of course). Checking each fuse (by pulling or direct measurement) will tell most problems except if you have a worn wire short on the hot side (positive) of the fuse box which is very unlikely.

Before you test for the parasitic drain be sure a wait 20 minutes after the car is off for the computers to shut down.
Hook up you ammeter in series with the negative battery cable to verify you have a draw.
The draw should be no more than 30 milliamps.
Check all you light bulbs to make sure they are off.
Then start pulling the fuses one by one.

Hello all. Just popping back in here after six years to see how things are going. Glad to see my DIY is still helping.

This was a good write up. Completed this yesterday.

Sent from my HTC VLE_U using Bimmer App

I just tried for an hour and a half and couldn't get the FSU out. I removed the plug with no problems at all but it seems my hand is simply too large to push the clip down and pull the FSU at the same time. I have no idea how anybody could reach behind it to get it out. I'd appreciate any fresh ideas on how to remove this thing.

Well, I got it out last night. I had to call my brother with much skinnier hands, he pulled it out using no effort at all. Problem solved, thanks Elvis.