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

Good for you!

Good for You!

Thanks for the info. Just replaced the FSU in my 2000 528i. Disconnecting the plug takes the most time. I used a small flathead screwdriver to help pry the plug out while pressing down on the plug and that seemed to work. Just make sure not to nick any wires with the screwdriver. Price for new FSU was only $36.04 online! Here is the link. http://www.******************.com/sk...gs+Best+Seller

I think the link was bad. just google Autoparts Warehouse. Part# REPB191504

Just done it this afternoon was quoted NZ 550 bought the part for NZ100 and fixed it in 60 minutes.
Brilliant help from the photo,s posted on this forum.
Thanks
Proud owner of a 2000 525i M

SAVED a BUNCH!!!!!!

Sir I am forever in your debt. Just replaced the final stage resistor in my BMW 520i and low and behold the heater burst into action for the first time in months!!! Part cost me a few euro on ebay. Absolutely delighted, was facing another harsh winter in Ireland without a heater in the car.
Thank you Thank you and thanks to these brilliant forums educating us wannabe mechanics.

A week later and it's still working - guess I fixed it correctly! Thank you soooooooo much for this thread. I was finally able to give the car back to my husband and get mine back. Can't thank you enough for your time and details on this DIY. Whoo-Rah!

I currently have this problem and could this drain the battery because my battery drains if i leave my car over 8 hours off and sometimes I hear the blower on with the car off and key out the ignition.

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!!!!!!!!!!!!!!!!!!!!!!!!!!

Originally Posted by JimLev

I have been reading and posting here for a while and also find that there is a lot of bum info given.
You can test the blower by unplugging the connector on the FSU and jumping a few pins together, this will make the blower run at full speed.

FSU connector pinout is this:
Pin 1 to blower motor
Pin 2 to 12 volts
Pin 3 to 0-5 VDC (this is the speed control input from the HVAC panel)
Pin 4 to ground
Pin 5 to blower motor

If you jump pin 1 and 2 together and also pins 4 and 5 together the motor will run if it is good.
Just make sure you don't touch pin 3.
You don't need to have the key on to check the blower motor, 12 volts is always at the FSU connector.

Originally Posted by cn90

1. Review this:
http://www.bimmerfest.com/forums/sho...75&postcount=3

On the FSR Connector itself, pins #1 and #5 feed the Blower Motor.
Apply 12 V to #1 and #5 terminals and the Blower should run, if not Blower Motor is bad.
(In BMW terminology 31 is usually ground, 15 is positive feed. So ground goes to SW/GN wire, and positive goes to RT/GN wire)




2. If you now confirm the Blower Motor is dead, then the DIY is here:
http://www.bimmerfest.com/forums/sho...d.php?t=343525

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 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.

The heat sink on the FSU is for the output transistor, which controls the fan speed, with a signal from the IHKA panel.

The part has undergone at least two changes: the heat sink is much different, providing much larger surface area to dissipate heat (that's why it's in the duct, in the air flow); and, the potting compound has been changed to a soft silicone (NOT silicon!) to allow for expansion. I suspect that the epoxy potting of earlier designs helped to destroy the circuitry, because it didn't allow for normal thermal expansion.

Is one of the symptoms of this the blower squeal noise (inside the car) when the car is first warming up? I'm wondering if maybe I'm just at an earlier stage of the "final stage" of this blower motor resistor going out. It’s never come on after the car is off so I’m not sure if it’s the resistor or the blower? My car is a 2001 BMW 530i with 61,000 miles.

i can't pull mine out. i got to the step where you unplug the wire and you pull it out. is there like a clip holding it or something cuz it moves right and left. it just wont come out and thank you in advance.

Originally Posted by ibz150

i can't pull mine out. i got to the step where you unplug the wire and you pull it out. is there like a clip holding it or something cuz it moves right and left. it just wont come out and thank you in advance.

See #538 above.

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.

Thanks to you all for the great posts and information on removing/replacing the FSR. I still have some problems - hoping somebody on here may be able to help. I had all of the classic symptoms of an FSR failure (fan on permanently etc.). I changed the FSR and everything seemed to work initially. However, when I was testing the fan speed control/operation of auto etc it failed again and the fan came on full power. Almost as though something in the control unit is blowing the FSR.... Any thoughts??

I joined this forum to thank you for this DIY repair. The blower had stopped working on my 2000 540i (265,000 Km), so searched the internet looking for a possible solution and found this thread.
I just completed this repair and it worked. The only difficult part of the repair was removing the unit because of the small space and the difficult position you have to get into to be able to do the job. I could not push down on the clip and pull the unit out with one hand and I couldn't get both hands in the space. I had to insert a flat screwdriver between the unit and the clip and then pull out the unit. A little difficult when you're doing it by feel.
I bought the replacement on Ebay for $38, so it was a very economical repair. Thanks again.

Had the same issue. dealer wanted 350 to replace the unit. bought a used one on ebay for 30 dollars.

couple of things I will add.

1- remove the cover under the glove box. made it much easier.

2- have a good working light so that you can see what you are doing.

3- I struggled with the plug. after removing the glove box undercover, I was better able to grasp the plug and gradually pull it out.

4- be patient when pulling out the plug. gradual pressure... take your time.

5-pull out the FSU from behind. makes it easier to pull it out.

6-buy a sitronic FSU made in germany. don't buy other ones because they fail. here is a seller.
http://www.pelicanparts.com/cgi-bin/...5%32%38i%20%20

good luck!

Well it looks like my turn to repair this controller.

Thanks to all that contributed.

Hey man. just did this fix. went to the local scrap yard, paid £10 for the fsr, popped it in, job done in less than 10 mins. Easy because of your clear instructions. Thank you so much!!!
kris.

P.S. I will say that i found it easier to pull the FSR out with the plug still attached as it gave me something extra to grip.

I just finished removing the FSU and at first I thought something was wrong because I just could not press those clips together hard enough. The directions are correct and there is no extra room. I did like you said and looked at it then felt with my hand. I thought once I released the FSU I wouldn’t be able to angle it to remove it because the prongs are so long, but it pulled straight out and then I rotated it standing it straight up in the small space before I pulled it out between the blower vent. I still haven’t purchased the new part, so I can’t say that’s the problem but I’ll let you know.

it helps if you remove the carpet panel beside the FSU.......good luck!

Completed, a little awkward to get at but went according to instructions. Thank you!!