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#11
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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