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Root cause insight into the common BMW blower motor resistorfailures



 
 
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  #11  
Old March 21st 13, 04:04 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Bimmer Owner
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Posts: 58
Default Root cause insight into the common BMW blower motor resistorfailures

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?

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  #12  
Old March 21st 13, 04:14 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw
jim beam[_4_]
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Posts: 3,204
Default Root cause insight into the common BMW blower motor resistorfailures

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
  #13  
Old March 21st 13, 04:22 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Bimmer Owner
external usenet poster
 
Posts: 58
Default Root cause insight into the common BMW blower motor resistorfailures

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?

  #14  
Old March 21st 13, 04:22 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw
Nate Nagel[_2_]
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Posts: 4,686
Default Root cause insight into the common BMW blower motor resistorfailures

On 03/21/2013 10:41 AM, jim beam wrote:
> 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>



link times out?

>
> 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.


ooh, or what? ITG gonna kick my ass? Sorry, I'm more interested in
helping the OP than your delicate little feelers.

>>
>> 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.
>


WTF is that supposed to mean?

OP can dissect the thing all he wants but it doesn't do him a damn bit
of good to know *what* has failed unless he knows *why* it failed.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  #15  
Old March 21st 13, 04:45 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Scott Dorsey
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Posts: 3,914
Default Root cause insight into the common BMW blower motor resistorfailures

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."
  #16  
Old March 21st 13, 04:57 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Bimmer Owner
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Posts: 58
Default Root cause insight into the common BMW blower motor resistorfailures

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.

  #17  
Old March 21st 13, 05:00 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Bimmer Owner
external usenet poster
 
Posts: 58
Default Root cause insight into the common BMW blower motor resistorfailures

On Thu, 21 Mar 2013 08:14:12 -0700, jim beam wrote:

> it's cheaper to just buy a new one.


To be clear, that's what 99.99999999% of the BMW owners do.
But that's not the point of this thread.

The point of this thread is to get a handle on WHY they are all
failing.

Specifically, how to figure that out is the question.

  #18  
Old March 21st 13, 05:04 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Bimmer Owner
external usenet poster
 
Posts: 58
Default Root cause insight into the common BMW blower motor resistorfailures

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?

  #19  
Old March 21st 13, 05:46 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Ismo Salonen
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Posts: 1
Default Root cause insight into the common BMW blower motor resistorfailures

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
  #20  
Old March 21st 13, 08:05 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw
Scott Dorsey
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Posts: 3,914
Default Root cause insight into the common BMW blower motor resistorfailures

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."
 




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