Root cause insight into the common BMW blower motor resistor failures

Page 7 of 9  
On Wed, 27 Mar 2013 09:16:55 -0400, Scott Dorsey wrote:

I will try this morning. (I was away on a trip for the past two days).
PS: Had to look up araldite: http://en.wikipedia.org/wiki/Araldite
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's an epoxy resin filled with silica. It will come off with DMSO at three atmospheres or so. Sometimes a soak in DMSO for a couple weeks will make it peel off. This will also soften the PC board though. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Bimmer Owner" wrote in message wrote:

Someone had scoped the whole board, and it was DC voltage everywhere (according to that reference). It's pretty clear there is no PWM.
The 16-pin surface mount chip seems to be a automotive temperature compensated voltage regulator with a huge voltage range, according to a lookup of the part number on it.
Here is the Elmos 10901D chip of my FSU as I cut it open today.

I wish there was a way to get rid of that heavy fibrous plastic goop! (What is that black fibrous tough stuff anyway?)
I have had good luck removing the stuff used on motorcycle voltage regulators that were potted soaking in MEK Methyl ethyl ketone (spelling?). Potent stuff. Use outdoors and keep your hands out of it. WW
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I don't know what it actually is but at work we desolved a potted firing system for a boat motor with something called OCP. Really stinks. Don't think I would want it in a car after it was used.
--
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/4/2014 8:09 PM, Ralph Mowery wrote:

My electronic assembly company built the electronic control unit for BMC Chopper of Bend, Oregon. Now defunked. We used two-part black epoxy that took 24 hours to completely cure. When applied it was water thin. Had to prep the box with RTV to keep the potting from running out around the connectors.
Paul
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, February 4, 2014 10:24:26 PM UTC-5, WW wrote:

Well, if that's the case, it would explain why they run so hot.

What lookup? No one has a datasheet on it. The most I've seen is the garbled Russian traslation of God knows what that someon posted earlier in the thread that says that's what it is.
It doesn't appear to me to be a standard part. Elmos is a large manufacturer of ASICs and that's probably what it is, ie a part done for whoever made the original. That would explain why there is no datasheet. But if that's so, an interesting question remains. How are all the various companies that make this thing getting the same part? If you make an ASIC with a semiconductor company, then unless you let them sell it to someone else, it's yours exclusively.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wednesday, February 5, 2014 4:50:11 PM UTC-5, snipped-for-privacy@optonline.net wrote :

This seems to confirm that it is indeed an ASIC part:
http://www.bimmerfest.com/forums/showthread.php?pt29514
Translation: Received a response from tehpodderzhi Elmos, cultural refused. ENGLISH: Thank you very much for your interest in our products. Unfortunately we are strictly not allowed to provide any information concer ning the E109.01D to you as this product is customer specific. Best regards, Sina Staufenberg staatl. geprüfte Betriebswirtin (Recht)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 26 Mar 2013 15:30:41 +0000, Bimmer Owner wrote:

Here is a picture of the BMW E39 HVAC/IHKA controller and sampling fan.

I'm googling for specs as we speak.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well, that's about what you need to know. Game over. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 22:54:59 +0000 (UTC), Bimmer Owner

So the crafty germans are using a high tech solid state resistor instead of a PWM speed controller???
If I had one and it blew I think I'd be designing a PWM controller to take it's place. Need to find out what kind of signal the controller expects, but that shouldn't be too difficult.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mar 21, 8:08 pm, snipped-for-privacy@snyder.on.ca wrote:

The dopes at BMW aren't any better at PWM's either. They use a PWM signal to control the aux fan on the radiator. You, know, the one that comes on if the cooling temp gets too high or the AC is on, etc. Apparently just a simple on/off motor wasn't good enough. So they made another one of their German electronic miracle gadgets that's part of the fan motor. That's right, electronics sitting right next to the hot radiator.....
On the TV show All in The Family, the meathead was arguing about Nixon and Watergate with Archie. Archie told the meathead that Nixon's mistake was when it involved electronics, ie bugging, taping, etc, that he should have used the Japanese, not Germans, ie Haldeman, Ehrlichman, etc. I think Archie was on to something.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 22:54:59 +0000 (UTC), Bimmer Owner

Hmm, it did look like it had quite a heat sink. I had assumed it used PWM to change speed, which should not generate much heat but my assumption might be wrong (or my understanding of PWM...) A solid state design that gets hot on purpose seems like a poor design to me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bimmer Owner wrote:

It should generate less heat at low speeds, if it is PWM.
--

Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

hread.php?tg8534&highlight=fsu

If it's just a typical DC motor with two leads, apply 12V and it should run full speed. You could also measure how many amps it draws when running. That is, IF it's just an ordinary motor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 22 Mar 2013 08:37:14 -0700, snipped-for-privacy@optonline.net wrote:

That makes a lot of sense!
Plus, it's easier to hook up leads to the harness connector than it is to get a DMM lead on the impossibly hard-to-get-to 40Amp Fuse F76 for the blower motor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motors are not just a resistive load though.
--
Clive

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 20 Mar 2013 23:17:36 -0700, jim beam wrote:

That's exactly what we've done - yet - we need help since nobody to date has figured out HOW to test an FSU that is fried. http://www.bimmerfest.com/forums/showthread.php?tg8534
Note: It appears to be an active component, but it probably does dissipate 100W.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 21 Mar 2013 03:08:09 +0000 (UTC), Bimmer Owner
Root cause insight into the common BMW blower motor resistor failures:

http://www.bimmerfest.com/forums/attachment.php?attachmentid 6060&d94115994
This is a design feature of BMWs. It's one of many whose purpose is to economically support BMW dealers with $$ from the fools dumb enough to buy a BMW.
"A fool and his money are soon parted".
As well they should be.
Enjoy your ride.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thursday, March 21, 2013 3:08:09 AM UTC, Bimmer Owner wrote:

FSU failure that plagues almost every 1997 to 2003 BMW? http://www.bimmerfe st.com/forums/attachment.php?attachmentid6060&d94115994 Also, doe s anyone have an idea HOW TO TEST a "repaired" FSU? The "blower motor resis tor", which also goes by FSR (Final Stage Resistor) or by FSU (Final Stage Unit), is known to fry itself in almost every single E46 (3-series), E39 (5 -series), and E38 (7-series) BMW. http://www.bimmerfest.com/forums/showthre ad.php?t3393 The problem with replacing this ~$100 part is that the ne w replacement FSU fries itself just as often as the old one did, so you end up repeatedly replacing your fried FSU every few years or so. http://www.b immerfest.com/forums/showthread.php?tR8566 That's fine for most people (although the DIY is a PITA) - but I ask this newsgroup whether anyone has any insight into WHAT is actually breaking - and - why? http://www.bimmerfe st.com/forums/showthread.php?t09399 Here is the best (admittedly sketch y) wiring diagram we have so far: http://www1.picturepush.com/photo/a/12467 819/img/12467819.png
My guess is this is the motor speed control and that it is ANALOG. This mea ns the resistance of the transistor varies with the speed. It gets hotest w hen the transistor is somewhere between full on and full off. At full on or full off the resistance of the transistor is either nearly infinent or clo se to being a short. In these conditions not much heat is disipated by it. I would design a pulse width modulated controller. This controls the curr ent to the motor in a digital fashion by switching the power off and on to the transistor is either in the fully off or fully on state. I have seen su ch circuits on the internet just by googling PWM motor controller. They are very simple to build with a big power FET and an NE555 oscilator also very cheap. Adapting it to the existing controls would be your problem. The goo gled articles will also tell you a lot more about how and why they work mor e efficently than an analog controller than I am willing to here.
Jimmie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Followups set to sci.electronics.repair .

At a guess, one or both of the big power transistors that are inside the FSU are failing. If the failure is that the blower motor doesn't run at all, they are probably failing open. If the failure is either that the blower motor runs at maximum speed, or a fuse blows, then they are probably failing shorted. The blower motor probably draws more current as it ages, and it may eventually be exceeding the power-handling capability of the transistor(s). When the motor is switched off, it may also generate a bit of a voltage spike, which may be above the voltage rating of the transistor(s).
A possible solution is to replace the transistor(s) with ones with a higher power rating in the same package. Another approach is to improve the heat-sinking, maybe by adding metal to the existing fins. Or, cut off the existing fins, bolt it to a huge slab of metal, and relocate the entire thing away from the blower duct.
As a crutch, you could drop the voltage to the FSU a little bit. This would slow down the blower, but also might tend to keep the voltages and currents down to what the transistors can handle. You would need to know the maximum current you would expect the FSU to draw; this probably happens when the charging system voltage is at is maximum, the blower motor is stone cold, and you turn it from "off" to "max". Then, buy a big rectifier diode with a rating of a few amps more than that, and splice it in to the power wire to the FSU. This will drop the voltage by a volt or two all the time. Or, you could put a power resistor in line instead; this will cause a variable voltage drop depending on how much power the FSU and blower is drawing at the time.
Keep in mind that in the winter, keeping the windshield clear is a safety function, so don't drop the blower speed too much.

The tricky part depends on the nature of the control signal to the FSU. If it's a simple analog voltage, that is easy to generate on the bench with a potentiometer. If it's some kind of digital bus (CAN?), it is *possible* to generate that on the bench, but it's probably easier to get the dashboard heater control out of a junked car and let it generate the signal.
To load the FSU, you can either use a power resistor that draws about the same amount of current as the blower motor on "high" (a headlight lamp might qualify), or an actual blower motor. The resistor will be "better behaved" than a real motor.
For a power supply, it depends on how much current the blower motor needs. You can get relatively inexpensive 13.8-volt power supplies in ranges up to several amps, designed for running "12 V" equipment on the bench. Samlex is one manufacturer but there are others. If it needs more than 10 A or so, it's probably cheaper to just use a real car battery and charge it when it's not being used.
You should probably arrange it so that there is some air blowing on the FSU under test. If you are using a real blower motor, you can make a duct out of cardboard. If not, use something like a 12 V computer case fan to move a little air across the FSU.
It may also be interesting to have some kind of thermometer on the FSU case while it is under test.
A good way to figure out what the FSU is actually doing is to probe a working car with an oscilloscope. This will show you immediately how the FSU is controlling the blower motor speed, as well as what the control signal looks like. You can stick a straight pin *through* the wire insulation as a test point, and then seal up the hole with electrical tape or silicone sealant.
As has been mentioned, it would be also interesting to cut one of the blower wires and measure the current drawn by the blower motor. For extra credit, do this on a new car (or a newly-installed blower motor) and then compare to a blower motor in a car that has just had its FSU fail.

On one hand, you would like stuff not to break. On the other hand, spending $100 every two or three years on a car that starts around $36,000 new is maybe not out of the realm of possibility. (Perspective: that's one tire or 25 to 30 gallons of gas.)
These cars are apparently sold worldwide. If the FSUs sell for cheaper in a lower-cost country, enough to offset shipping and taxes, import a box full of them and make money. :)
Matt Roberds
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.