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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. -- 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. -- 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 |
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? |
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 |
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? |
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 |
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." |
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. |
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. |
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? |
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 |
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." |
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." |
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." |
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 |
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? |
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. |
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. |
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). |
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. |
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 |
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 |
Root cause insight into the common BMW blower motor resistorfailures
On Thu, 21 Mar 2013 21:56:49 +0000, mroberds wrote:
It may also be interesting to have some kind of thermometer on the FSU case ... That seems like an EXCELLENT idea, if we can put some kind of temperature indicator in the FSU tines, then we can observe what the temperature is in situ - which might tell us something about what is overheating these things (assuming heat is the culprit). |
Root cause insight into the common BMW blower motor resistor failures
On Thu, 21 Mar 2013 16:59:01 -0400, "tm"
wrote: "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 Just put your ammeter into the heater blower fuse connector and you get the current of the blower motor. |
Root cause insight into the common BMW blower motor resistor failures
"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 |
Root cause insight into the common BMW blower motor resistor failures
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. |
Root cause insight into the common BMW blower motor resistor failures
On Mar 21, 5:58*pm, Ashton Crusher wrote:
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. That isn't necessarily the case. For example,t hey could be correctly designed, rated for the application, etc but have a manufacturing defect in just one of the components. A better questions is why BMW apparently doesn't give a damn to do the failure analysis to find out what's wrong. I have a friend who has an X5 and had this problem with the blower resistors. Even worse, the only symptom was it was draining the battery and it took a huge number of hours to track it down. While you're all wondering about that problem, might as well add the fancy aux radiator fan to the list. This car had that go and now the replacement one has failed again. And the symptom there is, again, it drains the battery even when the car is off. That fan is a real POS. Instead of just a simple fan motor, it's a fan that's variable speed, driven by a PWM signal. So, instead of just a motor, that fan sitting in front of the hot radiator has electronics in it. A real genius of a design. And for what? Like the fan can't just be on or off? Only reason I can think of is that they want to save a few watts of power to try to get better fuel economy. And for that their customers get to shell out $500 for a new fan every few years. |
Root cause insight into the common BMW blower motor resistor failures
On Mar 21, 8:08*pm, wrote:
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. The dopes at BMW aren't any better at PWM's either. They use a PWM signal to control the aux fan on the radiator. You, know, the one that comes on if the cooling temp gets too high or the AC is on, etc. Apparently just a simple on/off motor wasn't good enough. So they made another one of their German electronic miracle gadgets that's part of the fan motor. That's right, electronics sitting right next to the hot radiator..... On the TV show All in The Family, the meathead was arguing about Nixon and Watergate with Archie. Archie told the meathead that Nixon's mistake was when it involved electronics, ie bugging, taping, etc, that he should have used the Japanese, not Germans, ie Haldeman, Ehrlichman, etc. I think Archie was on to something. |
Root cause insight into the common BMW blower motor resistor failures
On Mar 20, 11:08*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...entid=126060&d... 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 I had a dodge caravan that fried its heater AC motor speed control resistor repeatedly.... the connector to the wiring harness detoriates from the high current and the voltage drop causes the connector to heat up and the entire assembly fails. Oddly enough I repair roll laminators that apply plastic film to paper think menus:) laminators experience similiar failures so I did the following. Purchased a new resistor block, soldered wires on all the connectors putting a heavy wire on each one.... Put a pigtail on each one. Installed resistor block. Its screwerd to the fire wall. Cut the plug assembly off the harness, stripped all wires, twisted them together and installed wire nuts on each one. had the van for years with zero problems for this part:) |
Root cause insight into the common BMW blower motor resistorfailures
On 03/21/2013 12:05 PM, Scott Dorsey wrote:
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. i'd rather repair light bulbs. 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. well, it cost me about $18 in parts to retrofit the linear dash light dimmer on my civic with a pre-built arduino unit. a custom unit could come in substantially less than that, if in sufficient quantity. -- fact check required |
Root cause insight into the common BMW blower motor resistorfailures
On 03/21/2013 09:00 AM, 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. i already told you - it's overheating. semiconductors don't like heat. Specifically, how to figure that out is the question. knowing how the light bulb blew doesn't fix it. -- fact check required |
Root cause insight into the common BMW blower motor resistorfailures
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