Does anyone have insight into what is the root cause (and repair) of the
FSU failure that plagues almost every 1997 to 2003 BMW?
http://www.bimmerfest.com/forums/att...0&d=1194115994

Also, does anyone have an idea HOW TO TEST a "repaired" FSU?

The "blower motor resistor", 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/sho...d.php?t=143393

The problem with replacing this ~$100 part is that the new 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.bimmerfest.com/forums/sho...d.php?t=528566

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.bimmerfest.com/forums/sho...d.php?t=309399

Here is the best (admittedly sketchy) wiring diagram we have so far:
http://www1.picturepush.com/photo/a/...g/12467819.png

On 03/20/2013 08:08 PM, Bimmer Owner wrote:
Does anyone have insight into what is the root cause (and repair) of the
FSU failure that plagues almost every 1997 to 2003 BMW?
http://www.bimmerfest.com/forums/att...0&d=1194115994

Also, does anyone have an idea HOW TO TEST a "repaired" FSU?

The "blower motor resistor", 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/sho...d.php?t=143393

The problem with replacing this ~$100 part is that the new 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.bimmerfest.com/forums/sho...d.php?t=528566

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.bimmerfest.com/forums/sho...d.php?t=309399

Here is the best (admittedly sketchy) wiring diagram we have so far:
http://www1.picturepush.com/photo/a/...g/12467819.png


that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

old resistor packs for fans were open wire that sat in the fan's air
stream for cooling. they were generally very reliable if their alloy
wasn't too susceptible to salt.

that unit looks like it still sits in the air stream with that honking
great heat sink and i estimate it's trying to dissipate 100W. that can
only mean it's a linear controller because a modern pwm device can
control high motor currents with very little heat dissipation 10W.

bottom line, a linear controller is always going to get hot and end up
frying itself over time. the only thing you can do is either replace it
with another unit that will ultimately meet the same fate, or undertake
a significant modification.

for the latter, you can try putting an even bigger heat sink on it - but
i doubt there's a lot extra room available. you can also "pwm" it. i
built a similar unit to deal with a linear controller over-heat issue on
my 89 civic.

http://www.flickr.com/photos/38636024@N00/5068043855
http://arduino.cc/en/Tutorial/PWM

depending on how much time you want to spend on a project like that, pwm
can control superbly and offers benefits like motor speed not being so
susceptible to supply voltage [engine idle voltage drop] etc.

the down side of pwm is that it can generate electrical noise. [poor
stereo installations can be particularly susceptible.] the ideal
solution is to implement pwm with "soft switching", but that's getting
quite advanced.


--
fact check required

On 03/20/2013 09:13 PM, jim beam wrote:
On 03/20/2013 08:08 PM, Bimmer Owner wrote:
Does anyone have insight into what is the root cause (and repair) of the
FSU failure that plagues almost every 1997 to 2003 BMW?

http://www.bimmerfest.com/forums/att...0&d=1194115994


Also, does anyone have an idea HOW TO TEST a "repaired" FSU?

The "blower motor resistor", 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/sho...d.php?t=143393

The problem with replacing this ~$100 part is that the new 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.bimmerfest.com/forums/sho...d.php?t=528566

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.bimmerfest.com/forums/sho...d.php?t=309399

Here is the best (admittedly sketchy) wiring diagram we have so far:
http://www1.picturepush.com/photo/a/...g/12467819.png


that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.



old resistor packs for fans were open wire that sat in the fan's air
stream for cooling. they were generally very reliable if their alloy
wasn't too susceptible to salt.

that unit looks like it still sits in the air stream with that honking
great heat sink and i estimate it's trying to dissipate 100W. that can
only mean it's a linear controller because a modern pwm device can
control high motor currents with very little heat dissipation 10W.

bottom line, a linear controller is always going to get hot and end up
frying itself over time. the only thing you can do is either replace it
with another unit that will ultimately meet the same fate, or undertake
a significant modification.

for the latter, you can try putting an even bigger heat sink on it - but
i doubt there's a lot extra room available. you can also "pwm" it. i
built a similar unit to deal with a linear controller over-heat issue on
my 89 civic.

http://www.flickr.com/photos/38636024@N00/5068043855
http://arduino.cc/en/Tutorial/PWM

depending on how much time you want to spend on a project like that, pwm
can control superbly and offers benefits like motor speed not being so
susceptible to supply voltage [engine idle voltage drop] etc.

the down side of pwm is that it can generate electrical noise. [poor
stereo installations can be particularly susceptible.] the ideal
solution is to implement pwm with "soft switching", but that's getting
quite advanced.




--
fact check required

that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

I see many Motor Speed Control Manufacturers upped their PWM
frequency to be between 16 K to 22 K to eliminate much of the noise.
Mikek

"amdx" wrote in message
...
that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

that doesn't of course get around the fact that the unit in question here
is apparently badly under rated, but the above does at least explain why
it's used.

I see many Motor Speed Control Manufacturers upped their PWM frequency
to be between 16 K to 22 K to eliminate much of the noise.
Mikek

That would also make the LPF very much smaller.

Even going to 40 to 60 kHz makes the magnetics smaller. We still do not know
what is under the PCB for that unit.

tm

amdx wrote:

that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

I see many Motor Speed Control Manufacturers upped their PWM frequency
to be between 16 K to 22 K to eliminate much of the noise.
Mikek
Sure, if you don't mind heating the motor up...

Jamie

On 03/24/2013 02:30 PM, Jamie wrote:
amdx wrote:

that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the
motor coils cause it to vibrate and make a humming noise at the pwm
control frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

I see many Motor Speed Control Manufacturers upped their PWM
frequency to be between 16 K to 22 K to eliminate much of the noise.
Mikek
Sure, if you don't mind heating the motor up...

Jamie


good point - how much? sure, big motor coils, big inductors -so how to
balance against pulse frequency for a bigger motor like a blower fan?


--
fact check required

On 03/24/2013 08:52 AM, amdx wrote:
that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

I see many Motor Speed Control Manufacturers upped their PWM
frequency to be between 16 K to 22 K to eliminate much of the noise.
Mikek

interesting.


--
fact check required

In article , jim beam wrote:

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

Yes, this is why you put an integrator stage after the pwm stage, so that
the motor sees nice filtered DC with very little of the PWM leftover.

Problem is that the integrator stage costs money and big electrolytics
tend to have limited life, so auto folks don't like doing that.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

It's a cheap, reliable way of doing the job, if it's done right. It's clear
that it wasn't done right, but I'm still waiting to hear what was done wrong.
Given all the RoHS-related failures and the report that touching up solder
joints on the transistors fixes the problem, I am suspicious that it's a
soldering issue made worse by the extreme temperature cycling.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 03/25/2013 06:59 AM, Scott Dorsey wrote:
In article , jim beam wrote:

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

Yes, this is why you put an integrator stage after the pwm stage, so that
the motor sees nice filtered DC with very little of the PWM leftover.

Problem is that the integrator stage costs money and big electrolytics
tend to have limited life, so auto folks don't like doing that.

you don't want to integrate the output, merely rub the shoulders off the
square waves to get the harmonics down. the whole point and benefit of
pwm is that you have full voltage full power available in each pulse.
that's how you can start and control a motor with high torque at low
rpm. if you integrate or smooth out the motor's supply, you effectively
lose that and the motor won't start or torque the same way or even at all.



that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

It's a cheap, reliable way of doing the job, if it's done right.

in this day and age, that's no longer true. motor control is one of the
hot ticket items on the silicon fab agenda, and has been for some time.
there are some great pwm options out there, and for not a lot of money.


It's clear
that it wasn't done right, but I'm still waiting to hear what was done wrong.
Given all the RoHS-related failures and the report that touching up solder
joints on the transistors fixes the problem, I am suspicious that it's a
soldering issue made worse by the extreme temperature cycling.

you definitely have a point there, but given the size and shape of that
heat sink, i don't think there's any way that silicon is getting
sufficient cooling, and is clearly way up against its ceiling. whether
that's accident or design is another matter, but the bottom line is that
it's an issue that spans multiple different module manufacturers across
multiple continents with different internal designs - that reduces the
probability of it being rohs and slaps it firmly into the vehicle
manufacturer's lap.


--
fact check required

In article , jim beam wrote:
On 03/25/2013 06:59 AM, Scott Dorsey wrote:
In article , jim beam wrote:

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the motor
coils cause it to vibrate and make a humming noise at the pwm control
frequency.

Yes, this is why you put an integrator stage after the pwm stage, so that
the motor sees nice filtered DC with very little of the PWM leftover.

Problem is that the integrator stage costs money and big electrolytics
tend to have limited life, so auto folks don't like doing that.

you don't want to integrate the output, merely rub the shoulders off the
square waves to get the harmonics down. the whole point and benefit of
pwm is that you have full voltage full power available in each pulse.
that's how you can start and control a motor with high torque at low
rpm. if you integrate or smooth out the motor's supply, you effectively
lose that and the motor won't start or torque the same way or even at all.

The more you rub off, the quieter the motor is! You start throwing stuff
in the KHz range into the motor, and it whines from magnetostriction.
The more of that you remove, the quieter it goes. Of course, if you make
it too quiet, people complain....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Mon, 25 Mar 2013 07:55:03 -0700, jim beam wrote:

that reduces the probability of it being rohs

What does ROHS mean?

Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?

On 03/21/2013 06:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?


My thought as well. Have you measured current draw on a new blower
motor and compared it to one that is installed in a car where the FSU
has failed? that would tell you whether there's any merit to this idea
or not.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

Nate Nagel wrote:
On 03/21/2013 06:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?

My thought as well. Have you measured current draw on a new blower
motor and compared it to one that is installed in a car where the FSU
has failed? that would tell you whether there's any merit to this idea
or not.

My inclination is to do exactly the same thing I do with the cooling system
issues: blame German engineers who seem to believe that their climate is
typical of the entire world.

I don't see why it is so hard to unpot one of these things and repair them
directly, especially if it's a semiconductor failure. Put a bigger transistor
in there.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 03/21/2013 06:47 AM, Scott Dorsey wrote:
Nate Nagel wrote:
On 03/21/2013 06:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?

My thought as well. Have you measured current draw on a new blower
motor and compared it to one that is installed in a car where the FSU
has failed? that would tell you whether there's any merit to this idea
or not.

My inclination is to do exactly the same thing I do with the cooling system
issues: blame German engineers who seem to believe that their climate is
typical of the entire world.

that's not going to fix it though. and the germans sell a LOT of these
vehciles in the middle east - it's a good deal hotter there than here.
they know exactly what they're doing.



I don't see why it is so hard to unpot one of these things and repair them
directly, especially if it's a semiconductor failure. Put a bigger transistor
in there.

unpotting is a nightmare - it will take much less time to build your own
pwm controller. who knows, maybe you can switch the existing unit???!!!


--
fact check required

In article , jim beam wrote:

I don't see why it is so hard to unpot one of these things and repair them
directly, especially if it's a semiconductor failure. Put a bigger transistor
in there.

unpotting is a nightmare - it will take much less time to build your own
pwm controller. who knows, maybe you can switch the existing unit???!!!

Unpotting is fun, it's a nice change in the day to just sit down for a couple
hours with a dremel tool and a dental pick.

But I agree, building an aftermarket controller replacement would not be
a tremendously difficult thing to do, and it might be a highly profitable
one.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Thu, 21 Mar 2013 09:47:31 -0400, Scott Dorsey wrote:

I don't see why it is so hard to unpot one of these things and repair them
directly, especially if it's a semiconductor failure.
Put a bigger transistor in there.

Here are pictures from the last half dozen who tried that approach:
http://www2.picturepush.com/photo/a/...g/12470740.jpg
http://www4.picturepush.com/photo/a/...g/12470742.jpg
http://www2.picturepush.com/photo/a/...g/12470745.jpg
http://www4.picturepush.com/photo/a/...g/12470747.jpg
http://www5.picturepush.com/photo/a/...g/12470748.jpg
http://www2.picturepush.com/photo/a/...g/12470750.jpg

Most who try to unpot fail, mainly due to damage caused to the
surface-mount circuit board during the initial mechanical degooping
step.

Those deft few who avoid knocking off the surface-mount components
with the debriding chisel, are left with a badly bruised board,
where some have said they've resoldered solder cracks (see pics).

One problem with "put a bigger xtor" is that nobody on this planet
has produced a decent circuit diagram of the FSU.

Does anyone here have access to an FSU circuit diagram?

On 03/21/2013 08:04 AM, Bimmer Owner wrote:
On Thu, 21 Mar 2013 09:47:31 -0400, Scott Dorsey wrote:

I don't see why it is so hard to unpot one of these things and repair them
directly, especially if it's a semiconductor failure.
Put a bigger transistor in there.

Here are pictures from the last half dozen who tried that approach:
http://www2.picturepush.com/photo/a/...g/12470740.jpg
http://www4.picturepush.com/photo/a/...g/12470742.jpg
http://www2.picturepush.com/photo/a/...g/12470745.jpg
http://www4.picturepush.com/photo/a/...g/12470747.jpg
http://www5.picturepush.com/photo/a/...g/12470748.jpg
http://www2.picturepush.com/photo/a/...g/12470750.jpg

Most who try to unpot fail, mainly due to damage caused to the
surface-mount circuit board during the initial mechanical degooping
step.

Those deft few who avoid knocking off the surface-mount components
with the debriding chisel, are left with a badly bruised board,
where some have said they've resoldered solder cracks (see pics).

if people priced their time and ignored the damage in which attempts to
unpot invariably result, it's cheaper to just buy a new one.



One problem with "put a bigger xtor" is that nobody on this planet
has produced a decent circuit diagram of the FSU.

Does anyone here have access to an FSU circuit diagram?

you don't need it any more than you need the circuit diagram of a chip's
internals - all you need is its function parameters - which you pretty
much already have.

you might be able to pwm the unit itself thus pretty much removing the
heat component thereby prolonging its life [literally] exponentially.


--
fact check required

Bimmer Owner wrote:
On Thu, 21 Mar 2013 09:47:31 -0400, Scott Dorsey wrote:

I don't see why it is so hard to unpot one of these things and repair them
directly, especially if it's a semiconductor failure.
Put a bigger transistor in there.

Here are pictures from the last half dozen who tried that approach:
http://www2.picturepush.com/photo/a/...g/12470740.jpg
http://www4.picturepush.com/photo/a/...g/12470742.jpg
http://www2.picturepush.com/photo/a/...g/12470745.jpg
http://www4.picturepush.com/photo/a/...g/12470747.jpg
http://www5.picturepush.com/photo/a/...g/12470748.jpg
http://www2.picturepush.com/photo/a/...g/12470750.jpg

These are kind of sloppy jobs. But it's clear there are two TO-3 devices
there which have been removed in all of those photos.

One problem with "put a bigger xtor" is that nobody on this planet
has produced a decent circuit diagram of the FSU.

Well, has anyone got docs on that mystery IC there? It's from Elmos
Semiconductor, but it's not a standard Elmos part number on it, so it's
almost certainly a custom, since it doesn't look like anything in their
standard book.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 03/21/2013 04:52 AM, Nate Nagel wrote:
On 03/21/2013 06:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?


My thought as well. Have you measured current draw on a new blower
motor and compared it to one that is installed in a car where the FSU
has failed? that would tell you whether there's any merit to this idea
or not.

for an "engineer", you're simply not of this planet.


--
fact check required

On 03/21/2013 09:55 AM, jim beam wrote:
On 03/21/2013 04:52 AM, Nate Nagel wrote:
On 03/21/2013 06:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?


My thought as well. Have you measured current draw on a new blower
motor and compared it to one that is installed in a car where the FSU
has failed? that would tell you whether there's any merit to this idea
or not.

for an "engineer", you're simply not of this planet.


Did you have any suggestions for the OP, or did you just show up to
snipe without contributing anything as per usual?

You do know that most electrical/electronic components have a maximum
current rating, yes? And that electric motors tend to draw more current
when the bearings are going or they are otherwise subjected to loads
higher than that for which they were designed? Does any of this sound
remotely familiar to you?

Really, what the will suggested seems to be a logical first step.

nate


--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On 03/21/2013 06:59 AM, Nate Nagel wrote:
On 03/21/2013 09:55 AM, jim beam wrote:
On 03/21/2013 04:52 AM, Nate Nagel wrote:
On 03/21/2013 06:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out. Change the
blower motor anytime?


My thought as well. Have you measured current draw on a new blower
motor and compared it to one that is installed in a car where the FSU
has failed? that would tell you whether there's any merit to this idea
or not.

for an "engineer", you're simply not of this planet.


Did you have any suggestions for the OP, or did you just show up to
snipe without contributing anything as per usual?

https://groups.google.com/group/rec.autos.tech/msg/1870e822d74b0a5c?dmode=source&output=gplain&noredi rect&pli=1

retard.



You do know that most electrical/electronic components have a maximum
current rating, yes? And that electric motors tend to draw more current
when the bearings are going or they are otherwise subjected to loads
higher than that for which they were designed? Does any of this sound
remotely familiar to you?

don't lecture me on electronics nate.



Really, what the will suggested seems to be a logical first step.

if you don't know what the **** you're doing and don't know how to use a
dvm.


--
fact check required

On 03/21/2013 03:55 AM, the will wrote:
Blower motor drawing too much amperage taking it out.

if it were an adequately designed unit, it should tolerate that and worse.


Change the
blower motor anytime?

analyze the actual problem - don't just waste money replacing stuff. a
$30 dvm will diagnose this for you, and you should already own one if
you have any ambition to repair any modern vehicle.


--
fact check required

On Wed, 20 Mar 2013 23:17:36 -0700, jim beam wrote:

analyze the actual problem - don't just waste money replacing stuff.

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/sho...d.php?t=678534

Note: It appears to be an active component, but it probably does
dissipate 100W.

On 03/21/2013 08:57 AM, Bimmer Owner wrote:
On Wed, 20 Mar 2013 23:17:36 -0700, jim beam wrote:

analyze the actual problem - don't just waste money replacing stuff.

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/sho...d.php?t=678534

it's like testing a dead light bulb.



Note: It appears to be an active component, but it probably does
dissipate 100W.

it dissipates Vd x Im where Vd = voltage drop across the unit output,
and Im = current drawn by motor. it will indeed get hotter when running
the motor slower because of the greater voltage drop across the unit.
that's why pwm is the better solution - the semiconductors are either
fully on [minimal heat dissipation] or fully off [minimal heat
dissipation]. the only time they get to dissipate heat is during
switching which is a sub-millisecond event and a tiny percentage of the
base time.


--
fact check required

On Thu, 21 Mar 2013 19:15:16 -0700, jim beam wrote:

that's why pwm is the better solution

Does pulse width modulation cause radio EMI?

On Thu, 21 Mar 2013 03:55:47 -0700, the will wrote:

Blower motor drawing too much amperage taking it out.
Change the blower motor anytime?

This is an interesting approach, given that the vast majority of
bimmer owners do NOT replace the blower motor - they replace the FSU.

While the blower motor replacement procedure is a major PITA, one
'can' test the leads from the FSU harness connector pins #5 and #1
which are power and ground respectively to the blower motor.

Again, we don't have a circuit diagram, but it has been said that
the blower motor takes about 6 amps (variously, depending on the speed)
but it would take a test jig to test that in operation.

To my knowledge, nobody has created that test jig (although I know
of only one attempt, which failed):
http://www.bimmerfest.com/forums/sho...&highlight=fsu

It's easy enough to test the resistance of the blower motor though,
and those results have come out at about 0.4 to 0.6 ohms.

It would be expensive to change a blower motor on a whim, so, how
would YOU suggest the blower motor be tested in situ?

Bimmer Owner wrote:

It's easy enough to test the resistance of the blower motor though,
and those results have come out at about 0.4 to 0.6 ohms.

Static resistance doesn't tell you anything, but operating current measured
with a DMM would tell you a lot.

It would be expensive to change a blower motor on a whim, so, how
would YOU suggest the blower motor be tested in situ?

I've never tested one, but I put a drop of turbine oil on the motor bearings
every five years or so. I do the same on the window and seat motors too.

I'd imagine if you listen carefully and have good hearing you can tell if the
motor is binding at all, but many people do not.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Thu, 21 Mar 2013 11:45:54 -0400, Scott Dorsey wrote:

Static resistance doesn't tell you anything, but operating current
measured with a DMM would tell you a lot.

It 'can' be done, but would require a test jig inserted inline
as the FSU is deeply ensconced under the dash while the blower motor
is even more deeply so.

I've never tested one, but I put a drop of turbine oil on the
motor bearings every five years or so.

While that preventive work might be prudent, the sheer effort
to remove the entire dash simply to access the blower motor
would be problematic.

Still, if the problem is that the blower motor is merely using more
current as it gets older, why wouldn't a NEW FSU burn up within a
few weeks of insertion?

On 03/21/2013 06:04 PM, Bimmer Owner wrote:
Still, if the problem is that the blower motor is merely using more
current as it gets older, why wouldn't a NEW FSU burn up within a
few weeks of insertion?
If the unit is near its limits it might just get very hot and parts
start aging very fast - semiconductors will just fail after a little
while. The new unit should fail sooner than the old one but who knows
who soon, maybe after a few years. Peugeot's ( and Citroen) used just
one huge pnp darlington which failed quite often , it was working too
near its operating limits.

(just my 2 cents)
ismo

Bimmer Owner wrote:
On Thu, 21 Mar 2013 11:45:54 -0400, Scott Dorsey wrote:

Static resistance doesn't tell you anything, but operating current
measured with a DMM would tell you a lot.

It 'can' be done, but would require a test jig inserted inline
as the FSU is deeply ensconced under the dash while the blower motor
is even more deeply so.

I don't know the wiring diagram on that particular model, so I don't know
where you would need to break in to measure just the current of the blower
without anything else. But it does not seem terribly insurmountable,
especially seeing that BMW is very good about breaking everything out into
connectors all over.

I've never tested one, but I put a drop of turbine oil on the
motor bearings every five years or so.

While that preventive work might be prudent, the sheer effort
to remove the entire dash simply to access the blower motor
would be problematic.

Well, that's partly why I drive a 2002 and an E28, everything is much
easier to get to.

Still, if the problem is that the blower motor is merely using more
current as it gets older, why wouldn't a NEW FSU burn up within a
few weeks of insertion?

You would expect that, indeed.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Thu, 21 Mar 2013 15:22:42 +0000 (UTC), Bimmer Owner
wrote:

On Thu, 21 Mar 2013 03:55:47 -0700, the will wrote:

Blower motor drawing too much amperage taking it out.
Change the blower motor anytime?

This is an interesting approach, given that the vast majority of
bimmer owners do NOT replace the blower motor - they replace the FSU.

While the blower motor replacement procedure is a major PITA, one
'can' test the leads from the FSU harness connector pins #5 and #1
which are power and ground respectively to the blower motor.

Again, we don't have a circuit diagram, but it has been said that
the blower motor takes about 6 amps (variously, depending on the speed)
but it would take a test jig to test that in operation.

To my knowledge, nobody has created that test jig (although I know
of only one attempt, which failed):
http://www.bimmerfest.com/forums/sho...&highlight=fsu

It's easy enough to test the resistance of the blower motor though,
and those results have come out at about 0.4 to 0.6 ohms.

It would be expensive to change a blower motor on a whim, so, how
would YOU suggest the blower motor be tested in situ?


If one replaces one of these perhaps it would be advisable to put a
fuse in the blower motor lines (it sounds like those can be gotten to
easily unlike the motor itself). If it's being blown by intermittent
high current draws the fuse could protect the $100 FSU. Another
option would be, at least for those who can live without the highest
blower setting and who think excess current draw is the culprit, would
be to put a power resistor in the blower motor line to limit the
current a bit. On the cheap pedestrian cars I drive the whole speed
control is just a trio of power resistors placed in the air flow to
help cool them. If they burn out (which is rare) they can sometimes
be fixed with a pop rivet.

On Thu, 21 Mar 2013 15:03:45 -0700, Ashton Crusher wrote:

If it's being blown by intermittent high current draws the
fuse could protect the $100 FSU.

That's an interesting idea. The FSU supposedly consumes the
most power when the blower motor is set to the LOW settings
(simply because it has to dissipate the power as heat), so,
we could prevent excess current by fusing... say with a 10A
fuse, the blower motor (which is said to consume 5 to 6 A).

"Bimmer Owner" wrote in message
...
On Thu, 21 Mar 2013 15:03:45 -0700, Ashton Crusher wrote:

If it's being blown by intermittent high current draws the
fuse could protect the $100 FSU.

That's an interesting idea. The FSU supposedly consumes the
most power when the blower motor is set to the LOW settings
(simply because it has to dissipate the power as heat), so,
we could prevent excess current by fusing... say with a 10A
fuse, the blower motor (which is said to consume 5 to 6 A).


Are you sure it is not already a pulse width regulator? Those transistors
look like they are TO-220 packages, not TO-3.
PWM has been around longer than SMT parts.

Maybe it is transients from the motor that are causing the failures.

Another place you could measure the current is by putting an ammeter in
place of the blower motor fuse.


tm

On Thu, 21 Mar 2013 22:54:59 +0000 (UTC), Bimmer Owner
wrote:

On Thu, 21 Mar 2013 15:03:45 -0700, Ashton Crusher wrote:

If it's being blown by intermittent high current draws the
fuse could protect the $100 FSU.

That's an interesting idea. The FSU supposedly consumes the
most power when the blower motor is set to the LOW settings
(simply because it has to dissipate the power as heat), so,
we could prevent excess current by fusing... say with a 10A
fuse, the blower motor (which is said to consume 5 to 6 A).
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 Thu, 21 Mar 2013 22:54:59 +0000 (UTC), Bimmer Owner
wrote:

On Thu, 21 Mar 2013 15:03:45 -0700, Ashton Crusher wrote:

If it's being blown by intermittent high current draws the
fuse could protect the $100 FSU.

That's an interesting idea. The FSU supposedly consumes the
most power when the blower motor is set to the LOW settings
(simply because it has to dissipate the power as heat), so,
we could prevent excess current by fusing... say with a 10A
fuse, the blower motor (which is said to consume 5 to 6 A).

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.

Bimmer Owner wrote:

On Thu, 21 Mar 2013 15:03:45 -0700, Ashton Crusher wrote:

If it's being blown by intermittent high current draws the
fuse could protect the $100 FSU.

That's an interesting idea. The FSU supposedly consumes the
most power when the blower motor is set to the LOW settings
(simply because it has to dissipate the power as heat), so,
we could prevent excess current by fusing... say with a 10A
fuse, the blower motor (which is said to consume 5 to 6 A).


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.

Sometimes Friday is just the fifth Monday of the week.

On Mar 21, 11:22*am, Bimmer Owner wrote:
On Thu, 21 Mar 2013 03:55:47 -0700, the will wrote:
Blower motor drawing too much amperage taking it out.
Change the blower motor anytime?

This is an interesting approach, given that the vast majority of
bimmer owners do NOT replace the blower motor - they replace the FSU.

While the blower motor replacement procedure is a major PITA, one
'can' test the leads from the FSU harness connector pins #5 and #1
which are power and ground respectively to the blower motor.

Again, we don't have a circuit diagram, but it has been said that
the blower motor takes about 6 amps (variously, depending on the speed)
but it would take a test jig to test that in operation.

To my knowledge, nobody has created that test jig (although I know
of only one attempt, which failed):http://www.bimmerfest.com/forums/sho...&highlight=fsu

It's easy enough to test the resistance of the blower motor though,
and those results have come out at about 0.4 to 0.6 ohms.

It would be expensive to change a blower motor on a whim, so, how
would YOU suggest the blower motor be tested in situ?

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.

On Fri, 22 Mar 2013 08:37:14 -0700, wrote:

If it's just a typical DC motor with two leads, apply 12V and
it should run full speed. You could [then] measure how many amps
it draws when running.

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.