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Root cause insight into the common BMW blower motor resistorfailures



 
 
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  #21  
Old March 21st 13, 08:16 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:
>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."
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  #22  
Old March 21st 13, 08:19 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:
>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."
  #23  
Old March 21st 13, 09:59 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
tm
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Posts: 22
Default Root cause insight into the common BMW blower motor resistor failures


"Scott Dorsey" > wrote in message
...
> 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.
>


Just measure the battery current with and without the blower running.

Turn every thing else off.


QED

  #24  
Old March 21st 13, 10:44 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 16:59:01 -0400, tm wrote:

> Just measure the battery current with and without the blower running.
> Turn every thing else off.


That's a pretty good idea.

Of course, it's impossible to turn everything off, as the computer
won't go to sleep for 16 minutes after the car is shut and armed,
but, still - with the blower consuming something like 5 or 6 amps,
we should be able to measure at least that.

The problem, even with the car's additional electronics powered up,
is HOW MUCH of a difference are we expecting between an older blower
motor current draw and a new one?

Are we looking for a 1 amp difference, for example?
  #25  
Old March 21st 13, 10:58 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Ashton Crusher[_2_]
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Posts: 2,874
Default Root cause insight into the common BMW blower motor resistor failures

On Thu, 21 Mar 2013 16:00:13 +0000 (UTC), Bimmer Owner
> wrote:

>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.


The simple answer is that they are under-designed for the conditions
under which they apparently are regularly subject to.
  #26  
Old March 21st 13, 11:03 PM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Ashton Crusher[_2_]
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Posts: 2,874
Default Root cause insight into the common BMW blower motor resistor failures

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.
  #27  
Old March 21st 13, 11:54 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 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).

  #28  
Old March 21st 13, 11:56 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 21:56:49 +0000, mroberds wrote:

> 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.


Actually, I was remiss in not stating that the blower motor generally
fails by acting weirdly, often said to "have a mind of its own", and,
most often by a parasitic current draw overnight that kills the battery.

  #29  
Old March 22nd 13, 12:07 AM posted to rec.autos.tech,sci.electronics.repair,alt.autos.bmw,alt.home.repair
Mark[_1_]
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Posts: 63
Default Root cause insight into the common BMW blower motor resistor failures


> > 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.

>


i guess they call replacing a simple resistor with a bunch of
transistors.... "progress"

i'd replace the module with a bunch of power resistors and maybe a PTC
(self resetting) fuse

Mark


Mark
  #30  
Old March 22nd 13, 12:08 AM 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 15:16:46 -0400, Scott Dorsey wrote:

> there are two TO-3 devices there which have been removed
> in all of those photos.


I don't know what a "TO-3" device is, but nobody removed anything
in those photos other than the goop that covered the circuit board.

> 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


Focusing just on that Elmos Semiconductor AG IC from this thread:
http://www.bimmerfest.com/forums/sho...d.php?t=309399
It looks like the PN is ELMOS, 10901D, 667A 1302A

It might be a generic or a special chip; I can't find it on the web:
http://www.elmos.com/produkte/automo...motor-ics.html

 




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