Root cause insight into the common BMW blower motor resistorfailures
 

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

Root cause insight into the common BMW blower motor resistorfailures
 

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.


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fact check required

Root cause insight into the common BMW blower motor resistorfailures
 

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

Root cause insight into the common BMW blower motor resistor failures
 

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

Root cause insight into the common BMW blower motor resistorfailures
 

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

Root cause insight into the common BMW blower motor resistorfailures
 

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."

Root cause insight into the common BMW blower motor resistorfailures
 

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.


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fact check required

Root cause insight into the common BMW blower motor resistorfailures
 

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

Root cause insight into the common BMW blower motor resistorfailures
 

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

Root cause insight into the common BMW blower motor resistorfailures
 

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