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.
"C'est un Nagra. C'est suisse, et tres, tres precis."
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
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
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.
On Wednesday, February 5, 2014 4:50:11 PM UTC-5, email@example.com wrote
This seems to confirm that it is indeed an ASIC part:
Translation: Received a response from tehpodderzhi Elmos, cultural refused.
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.
staatl. geprüfte Betriebswirtin (Recht)
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.
On Mar 21, 8:08 pm, firstname.lastname@example.org 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
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.
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.
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.
Note: It appears to be an active component, but it probably does
On Thu, 21 Mar 2013 03:08:09 +0000 (UTC), Bimmer Owner
Root cause insight into the common BMW blower motor resistor failures:
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.
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
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.
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
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
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. :)
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