BimmerFest BMW Forum banner

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

1M views 696 replies 440 participants last post by  rakitha92.p 
#1 ·
Does your A/C-heater blower seem like it's possessed? Does it quit working for no apparent reason, then come on again just as mysteriously? Does it run only at one speed no matter what the controls say? Does it keep running even when the car is off and the key is out of the ignition? Your problem is most likely a faulty final stage unit.

Based on what I've seen here and elsewhere, this is a chronic problem with the E39, but fortunately it's a relatively cheap and easy fix. There's a good DIY here, but since questions about it get posted here with regular frequency, I figured it would be a good idea to post one here too. Some of the photos in this post are very large because it's very helpful to see the details if you have no idea what's going on here.

BMW calls this thing the "final stage unit;" the parts guys call it a "blower motor resistor." I'm not sure what the reason for the different terminology is, but it's the same part. The PNs have changed a couple of times over the years, but as of the date of this posting, what you want is PN 64 11 6 923 204 and there's a diagram of the system here. As far as I can tell, the same part is used in all E39 models (but you may want to confirm this). Bavarian Autosport has them for about $70, but they're unfortunately available a lot of places, including the parts counter of your local dealership (I say "unfortunately" because it's a reflection of how often this thing fails).

For some reason, dealer service departments are notorious for not being able to recognize this issue, and may charge you for hundreds or thousands of dollars of unnecessary repairs without solving the problem. If you don't feel confident doing this yourself (i.e., you're the sort of person who is more likely to take an eye out with a screwdriver than a screw), at least bring them this information. Done properly, this is a 15-minute, ~$100 repair.

This is what you're replacing:


(Side view, with highlighter for scale)


(one end view)


(other end view)

The silver part of it is a heat sink. I'm not an electrical engineer, but I believe this thing allows the blower controls to change the speed of the blower by altering the current that passes through it. Inside is a bundle of resistors, and by sending the current through a different combination of leads, it creates the proper current to operate the blower at a desired speed. But resistors generate heat (thus the need for a heat sink), and over time, I suspect the constant heat up-cool down cycle degrades the resistors until they no longer produce the right current, and the controller can no longer send the right signals to the blower. Thus, the blower starts acting strangely despite what the controls are doing.

Now, I've read a lot of horror stories about how difficult this replacement can be, but I didn't find it that way at all. This is an extremely simple operation that took me less than 10 minutes. The hardest part was getting myself into a position where I could get at the faulty FSU.

All you need here is a Phillips screwdriver, a flashlight (the one in your glovebox will work fine) and understanding that you're working with electrical components, not mechanical ones. That means being mindful of how much force you're using. Nothing in this operation requires any great effort, so if you find yourself needing force things, you're doing something wrong.

The FSU is behind the dash in the passenger side footwell. You'll find it easier to work if you pull out the cover under the glovebox. It's not secured by anything, so just yank it out. The FSU is behind a fabric covered plastic panel on the left side:



You want to unscrew the screw (red circle), then slide the panel backward (see arrow), not out. It's also held in place by two metal clips that attach to the frame behind it:



Once you've got the panel out, lay on your back and look up at the space you've just exposed. The FSU is inside there.



Inside the space, you'll see a plug with 5 colored wires coming out of it. The FSU is the thing the plug is connected to, so you've got to get the plug out. The plug is held in place by two clips on the side, and you need to squeeze the clips to free it.



You may find the plug a bit difficult to get out; if so, just wiggle it back and forth until it comes free. Don't yank it out--you may break one of the wires loose, in which case you've just bought yourself an expensive and embarrassing trip to the dealer.

The FSU is itself held in place by another clip at the bottom. You need to push this clip down at the same time you're pulling the FSU out.


(note--plug is still in place in this photo, but take it out first. I didn't take a picture of the FSU with the plug out :rolleyes: )

Again, if you're doing it right, you should not need to force anything. Once free of the clip, the FSU should slide out easily.

You may find all of this easier if you lay on your back in the footwell to get your bearings, then sit up straight, reach under the dash, and do it "by feel."

Now, surprise, surprise, the part you've just removed won't resemble the new one exactly, since as I mentioned, the PNs have changed a couple of times:



Hmm, could this be because the original version was defective? :rolleyes: :dunno: :mad:

Now just slide the new one in the spot the old one came out of. It should slide into place with a "snap" as the clip engages it.



New FSU in place. Note orientation--it will only go in one way. If you're having trouble getting it in, you've probably got it rotated 90 or 180 degrees out of alignment.

Replace the plug, then slide the panel back in the way it came out. Be sure to get both clips into their respective slots, or it will hang loose. Replace the screw.

If you've done everything right, your blower should operate normally now. If it's not, go back in and check the connections. If everything looks right but it still doesn't work, you may have other problems.
 
See less See more
10
#233 ·
Can you detect a bad FSU from your OBD codes?

I'm still toying with the idea of OBD II freeware or buying an OBDII tester, especially one that provides real-time data wirelessly to my iPod touch that I connect to the DICE Silverline.

Doing OBDII research, I found this article which implies that you might be able to detect a bad FSU from the OBD2 codes.

Has anyone done that here?

Is this article saying you can detect a bad FSU with an OBD 2 scanner?
 

Attachments

#235 · (Edited)
Two lessons learned when removing the FSU in the 2002 E39!

It took me about 20 minutes.
It took me MUCH longer than 20 minutes to remove the FSU so that my monthly dead battery would be resolved (I hope).

The instructions here were great. But still it took me almost the entire Superbowl to get the FSU harness connector clip off, and, even then, I ended up breaking one of the sides of the clips to the 2002 FSU.

I concur with post #39 of this thread that it helps greatly to remove the underside of the glovebox (two clips).

I don't know if it's covered in this thread, but, after breaking the clip and examining why, I learned the following:

It is imperative you PUSH inward on the connector (towards the FSU) before you squeeze the clips (perpendicular to the FSU) to unclip!

Otherwise, it will break, like this!
 

Attachments

#236 · (Edited)
Here are the steps I should have used to remove and replace my FSU

As always, I took pictures but here are the text steps I recommend for removing and replacing the 2002 E39 FSU.

0. Get a flashlight, a #2 Philips screwdriver + a set of 6-inch needlenose pliars
1. Move the passenger seat back & lay the backrest down as far as it will go
2. Lie on your back, hands above your head, ready to work in the foot well
3. Remove the #2 Philips screw holding the passenger left-food kick panel
4. Slide this kick panel straight back (toward the rear of the car) to unclip
5. Slide the underside of the glove box straight back (two clips, no screws)
6. Locate the FSU harness connector and put your pliars on the two "ears"
7. PUSH (this is the important part) a millimeter or less inward, & then unclip
(Note: Step 7 took me all of the Superbowl & even then I broke a clip ear!)
8. Once the FSU connector is off, push on the one FSU connector to release
9. Pull out the old FSU and measure resistance from each terminal to the aluminum fins
10. Measure the resistance of the new FSU's terminals to the aluminum fins
11. As they say, assembly is the reverse of disassembly
12. Test the A/C & air & especially listen for fans after the key is pulled out

RESISTANCE FROM TERMINAL TO ALUMINUM FINS:
#4 #5
#1 #2 #3

pin 1 OLD: 600 K ohm NEW: 11.2 ohms
pin 2 OLD: 3.02 M ohm NEW: 1.22 M ohm
pin 3 OLD: 2.219 M ohm NEW: 608 K ohm
pin 4 OLD: 2.136 M ohm NEW: 602 K ohm
pin 5 OLD: 3.05 M ohm NEW: 1.277 M ohm
 

Attachments

#449 ·
:thumbup:
As always, I took pictures but here are the text steps I recommend for removing and replacing the 2002 E39 FSU.

0. Get a flashlight, a #2 Philips screwdriver + a set of 6-inch needlenose pliars
1. Move the passenger seat back & lay the backrest down as far as it will go
2. Lie on your back, hands above your head, ready to work in the foot well
3. Remove the #2 Philips screw holding the passenger left-food kick panel
4. Slide this kick panel straight back (toward the rear of the car) to unclip
5. Slide the underside of the glove box straight back (two clips, no screws)
6. Locate the FSU harness connector and put your pliars on the two "ears"
7. PUSH (this is the important part) a millimeter or less inward, & then unclip
(Note: Step 7 took me all of the Superbowl & even then I broke a clip ear!)
8. Once the FSU connector is off, push on the one FSU connector to release
9. Pull out the old FSU and measure resistance from each terminal to the aluminum fins
10. Measure the resistance of the new FSU's terminals to the aluminum fins
11. As they say, assembly is the reverse of disassembly
12. Test the A/C & air & especially listen for fans after the key is pulled out

RESISTANCE FROM TERMINAL TO ALUMINUM FINS:
#4 #5
#1 #2 #3

pin 1 OLD: 600 K ohm NEW: 11.2 ohms
pin 2 OLD: 3.02 M ohm NEW: 1.22 M ohm
pin 3 OLD: 2.219 M ohm NEW: 608 K ohm
pin 4 OLD: 2.136 M ohm NEW: 602 K ohm
pin 5 OLD: 3.05 M ohm NEW: 1.277 M ohm
 
#237 ·
It helps greatly to remove the underside of the glove box

It helped greatly to remove the additional underside panel below the glovebox.

This panel slides outward (horizontally, toward the back).

It's held in place with only two clips near the bulkhead and nothing else.
 

Attachments

#238 · (Edited)
As I said, the big lesson was that the FSU clips were extremely uncooperative but they finally yielded to pressure & persistence (it would have been nice to know the technique of pushing in first before pulling out but I only learned that in hindsight from examining the little tiny lip on the clip ear ends).

Here is the resistance measurement of the old FSU and new FSU for the 2002 E39. It would be of interest to get a database from all that follow us to see if there's a pattern.

I didn't know where to measure between so all measurements are from the terminals to the fins. Notice I arbitrarily numbered them from 1 to 5 in a clockwise direction starting from top left as the FSU was facing away from me. I think pin #1 (bottom left) is the ground pin (do you?).

Does anyone have a suggestion as to what to use to take the old FSU apart so we can have a macabre look inside?
 

Attachments

#239 ·
The old FSU is the original aluminum body; the new is black plastic

Well, this morning, on my way to work, the E39 started up perfectly.
No blower wierdities at all ... especially when I shut the car off.

To confirm what others have said, mine seems to have had the original FSU which is the larger cast-aluminum body while the new "Made in Germany" FSU is smaller and has a black plastic body.

 
#240 ·
Lesson learned .... PRESS DOWN and then press inward to unclip the FSU!

The biggest mistake I made, other than missing the entire Superbowl because it took me a couple of hours whereas I thought it would be done by halftime ... was to not push down on the harness connector (toward the FSU) while pressing the clips inward (perpendicular to the FSU).

As you can see, the method I used was too brutish for the FSU and one ear of the clip broke off.

It was only after examining the clip itself that I realized it has a teeeeny tiny lip of a fishhook on the end, which was the part, I think, I couldn't clear.

Lesson learned .... PRESS DOWN and then press inward to unclip the FSU!
 
#241 ·
I think you are all mistaken in pointing "jdelsesto" in the wrong direction. He isn't going to find his Final Stage Resistor in the passenger side footwell behind the center stack. He is driving an E38 740. The location of the Final Stage Resistor is actually attached to the heater blower motor itself. This is a very labor intensive job and will require a lot of time an patience to get at. Before even being able to replace anything you are probably looking at 4-6 hours. There is a whole step-by-step procedure on www.e38.org. Go down to the HVAC section and there is a link to remove the blower motor. If you are doing the FSR then you should pay the extra money as you are already in there and replace the blower motor itself as the labor already overlaps (if you are paying someone to do it). If you are opting to do it yourself, I would recommend doing it anyway so you don't have added hassle in the future.

If anyone knows of a REALLY well detailed DIY for this procedure the link would be greatly appreciated. Pictures, tools and parts required would be great. Most of the ones (including the aforementioned) that I have come across are pretty vague and basic. The cost for the parts isn't cheap either, but well worth the money.
 
#242 · (Edited)
We need to do an autopsy on the BMW FSU to figure out what is going wrong

I think we can consider pin #1 ground, and pin #2 12v power (notice that it's fused at a whopping 40 amps!).
I'm guessing #3 (x671) is an input to the FSU from the heating and a/c module.
I'm not sure what #4 (x18722) and #5 (X816) are but one or more of those leads must be going to the blower motor itself.

SUMMARY (I think):
#1 = ground
#2 = 12V power, 40 amp fused
#3 = input to fsu from heat/ac module
#4 = output power to the blower motor? (speed 1?)
#5 = output power to the blower motor (speed 2?)

 

Attachments

#243 ·
Final Stage Resistor - Complete Electrical Failure Cause?

Elvis, I just read your post regarding the final stage resistor and wanted to say thanks but to also ask if you know whether the final stage resistor could be responsible for a complete electrical shut down of my 2000 540ia. The dealership is suggesting that there is an 80% probability that the final stage resistor is the cause of my car having a complete electrical shut down while driving. I have tested the alt and it is charging at over 14 v and the battery is 3 days old. I've read about this type of shut down in posts at other sites but no causes. Do you or any ody else have any idea what would cause this type of electrical shutdown? FYi the car will often start again after a while but will again cut out unpredictably.

Thanks in advance.
 
#245 ·
Elvis, I just read your post regarding the final stage resistor and wanted to say thanks but to also ask if you know whether the final stage resistor could be responsible for a complete electrical shut down of my 2000 540ia. The dealership is suggesting that there is an 80% probability that the final stage resistor is the cause of my car having a complete electrical shut down while driving. I have tested the alt and it is charging at over 14 v and the battery is 3 days old. I've read about this type of shut down in posts at other sites but no causes. Do you or any ody else have any idea what would cause this type of electrical shutdown? FYi the car will often start again after a while but will again cut out unpredictably.

Thanks in advance.
Complete electrical shut down while the car is driving is almost certainly due to a loose battery terminal. Happened to me a month after I had the battery changed. The terminals certainly FELT tight, very tight. However, a shop removed and re-connected all terminals resulting in completely eliminating the problem. No problem in about 25k miles!
 
#247 ·
hey, thanks for the details on this. I have a 97 528 so it should all look like yours. something different with my scenario: there is no air blowing our of vents, cold nor hot. however, if i turn on the fan, there is a burned smell that comes through the vents. obviously something is pushing that smell out of the vents because as soon as i turn it off, the smell goes away. do you think theres something more to my problem than just the FSU?
 
#250 ·
Hey guys, this was a great post, thank you.
Has anyone had this problem yet....
- I replaced the FSU on my 2002 530i when I was having issues with the fan not turning off when the car was turned off. Using this post and the great step by step instructions the fix went smoothly and solved my problem. However it's now 2 months later and the FSU unit has gone out on me again. I now have my 2nd FSU (OEM) ordered for replacement. I guess the 1st FSU replacement could have been faulty. But, could there be anoth reason for this brand new FSU unit to fail after only a couple of months? I don't want to be replacing these guys every few months at about 100 bucks a pop.... I welcome any ideas.
Thanks.
 
#252 · (Edited)
#253 ·
FSU Replacement

Thanks for the update changed it and it works great. Your instructions were good and precise, however the parts is very hard to reach and the space is tight, so if someone is not handy then it is better to take it to a dealer. Total time needed if you know what you are doing is around 20/25 min.utes from start to finish
 
#254 ·
I called the dealership and explained the problem and told that It'd be 300 including labor, and an hour job. I already knew wat was needed to be changed. and asked the guy at dealership whether that was any recall with the resistor and explained no.

and Thank a lot for the descriptions on how to change the resistor. this certainly has saved me 200 bucks. I feel sorry for BMW dealers in this economically unstable time that they didn't get my business but in a way I'm sure that they'd learn not to rip people off for charging $35 in just labor to change the viperblade refills ( I was once charged that )..

Thanks agian.
 
#255 ·
I called the dealership and explained the problem and told that It'd be 300 including labor, and an hour job.
It took me at least an hour but if I only knew exactly which way to unclip the FSU, it would have taken fifteen minutes from start to finish.

Others seem to have had the same problem trying to figure out how to unclip the FSU. It's not so much the size of our hands (mine are small), but, the motions involved.

I think (see this post for more explicit detail), you have to both PUSH AGAINST THE FSU while unclipping (as if you're pushing it in even harder) and press out on the clips (the opposite of what you'd think).

I'm not exactly sure about the clips but I am pretty sure that it makes it easier to push in on the fsu (in the opposite direction) befure pressing on the harness clips themselves.

Anyway, I reference this thread for details. It might be nice if someone who has done it can explain the best way to unclip the damn thing! Hopefully I'll never need to do it again; but others will, for sure so the effort won't go wasted.

they didn't get my business but in a way I'm sure that they'd learn not to rip people off for charging $35 in just labor to change the wiperblade refills
OT but I filed a thread on the wiperblade refills. I wish I knew before I did it what I know now (see the thread for details).

Bluebee
 

Attachments

#256 ·
My friend dropped a dime into the cigarette lighter of my 528 and it blew my radio fuse and the climate unit stopped working. I changed the fuse for the radio and now it works but the heater doesnt. I changed the fuse for it too but it doesnt even come on. I replaced the fsu but that didnt help. I tried swapping ccu's with a friends 97 (mines a 99) But that didnt help. So pissed summers coming up and I dont got ac:cry: Anyone know what could be the problem?:hi: :flame:
 
#257 ·
Hey

We have had the intermittent blower speed up and down, up and down.. not matter what setting.. had this for a little while... when then had a dead battery after being parked for a day, the road side assist mob told us it was a dead cell in the battery.. new battery all ok for a few weeks, then dead battery again , in the same car park.. road side assist mob now say must be a faulty relay or something..

Lots of research let me to this site and it does sound like the FSU.

Called the local dealership, explained the problem and that I wanted the FSU replaced.. he seemed to have no idea on what I was talking about and wanted to run right thru the whole system to see if he can locate it..

So will now order the part from a local supplier but want to know if I can pop a fuse to stop the battery draining until we get the part?

Any advise would be great.

Cheers,

Steve
 
#258 ·
Right Hand Drive FSU

This is one dificult job from Sept 2000 onwards on RH drive models. You'll know if it has a black motor housing in front of the FSU. The stepper motor has 2 screws one being in the most imposible place to get out. One screw one takes 30 secs to get out, the second 2 hours!!!! You need a 20 torx that is about 6-8 inches long and isn't too bulky. You'll have to feel about on the top of the stepper motor as you can't see the screw at all. Will take 2 weeks for my arm and neck to recover. Silly thing is that the screw takes 3 turns and it's out! will take a picture of the stepper motor out as it may help someone in doing the job.
 
#259 · (Edited)
Right Hand Drive FSU

--------------------------------------------------------------------------------

This is one difficult job from Sept 2000 onwards on RH drive models. You'll know if it has a black motor housing in front of the FSU. The stepper motor has 2 screws one being in the most imposible place to get out. One screw one takes 30 secs to get out, the second 2 hours!!!! You need a 20 torx that is about 6-8 inches long and isn't too bulky. You'll have to feel about on the top of the stepper motor as you can't see the screw at all. Will take 2 weeks for my arm and neck to recover. Silly thing is that the screw takes 3 turns and it's out! will take a picture of the stepper motor out as it may help someone doing the job in the future.

Here's a link to the graphic of the stepper motor housing unit.

http://storeandshare.sky.com/invite...a-sky_gemini2&t=154b11f902bc73e5&r=mg&lang=en

I will also do a forensic on the FSU and post the information on the relevant forum topic.
 
#262 ·
FSU and Stepper Motor on Right Hand Drive

Right Hand Drive FSU

--------------------------------------------------------------------------------

This is one difficult job from Sept 2000 onwards on RH drive models. You'll know if it has a black motor housing in front of the FSU. The stepper motor has 2 screws one being in the most imposible place to get out. One screw one takes 30 secs to get out, the second 2 hours!!!! You need a 20 torx that is about 6-8 inches long and isn't too bulky. You'll have to feel about on the top of the stepper motor as you can't see the screw at all. Will take 2 weeks for my arm and neck to recover. Silly thing is that the screw takes 3 turns and it's out! will take a picture of the stepper motor out as it may help someone doing the job in the future.

PS Got some pictures of the stepper motor and housing unit but need somewhere to post them. Can anyone help out?

I will also do a forensic on the FSU and post the information on the relevant forum topic.
You are right, this is a very difficult job on some Right Hand Drive cars due to the stepper motor in front of the FSU!

Many thanks to the people who have posted advice on changing the Final Stage Resistor, without which I would not have gotten this far. My new Resistor has arrived and I have disassembled the car up to the FSU but cannot remove the stepper motor. Unfortunately I think I have broken part of the stepper motor. There is a small rectangular plug that should be pressed and then pulled out of the stepper motor, but I have pulled the plug together with part of the round piece off the base of the stepper motor. It has exposed about 4 silver pins and what looks like very fine copper wire. I have done a search on RealOEM and the stepper motor part seems to be called a 'positng. drive, fresh air recirc. (Part 64116934823)'. Does anyone know more about this part and where it is available from in the UK?

Any help on this would be most appreciated.
 
#261 · (Edited)
Put unit in today. everything works fine. Unit was £20 from ebay. So lots of money saved here!.

And, here is what I measured between each pin and ground (the FSU body):
#1: Old FSU = 6.6 ohms, new FSU = 10 ohms
#2: Old FSU = 0 ohms, new FSU = 1000 Kohms
#3: Old FSU = 0 ohms, new FSU = 900 Kohms
#4: Old FSU = 0 ohms, new FSU = 600 Kohms
#5: Old FSU = 0 ohms, new FSU = 1674 Kohms
 
#278 ·
Put unit in today. everything works fine. Unit was £20 from eBay. So lots of money saved here!.

And, here is what I measured between each pin and ground (the FSU body):
#1: Old FSU = 6.6 ohms, new FSU = 10 ohms
#2: Old FSU = 0 ohms, new FSU = 1000 Kohms
#3: Old FSU = 0 ohms, new FSU = 900 Kohms
#4: Old FSU = 0 ohms, new FSU = 600 Kohms
#5: Old FSU = 0 ohms, new FSU = 1674 Kohms


For comparison, I have my new unit measured today. Counting from the bottom 3 pins to the upper 2 pins. Pin #1 is the bottom left one. Measurements are to the unit's "fingers".

#1. 0 Kohms
#2. 1205 Kohms
#3. 600 Kohms
#4. 595 Kohms
#5. 1205 Kohms

It seem like pin #1 is the unit's "fingers". I therefore continued to measure the values between each on of the pins: ("2-3" means the measurement between pin #2 and #3.)

2-3: 635 Kohms
2-4: 611 Kohms
2-5: 0 Kohms

3-4: 23 Kohms
3-5: 630 Kohms

4-5: 608 Kohms

No measurement for the old unit. It's still in the car... ;)

mw
 

Attachments

#263 ·
I can get you one (64116934823) from the local dealer. You can pay me by paypal if interested. The cost from the dealer is £48.00 and I can post for £2.00. I am going to dealer on Tues next to pick up a housing unit and have checked and they have one. Let me know if interested as it seems a bit expensive.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top