Root cause insight into the common BMW blower motor resistorfailures

Have you got a link to these "common problems" you keep posting about?


"Bimmer Owner" > wrote in message
...
> 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

=========

> Almost every BMW E39 (5-series) and E38 (7-series) and E46 (3-series)
> has shorts that develop in the trunk wiring loom - all in the same spot!

I think it's already been suggested, but if the car were my own vehicle, I'd
be content with a multi-position switch for the blower motor.. this is a
very reliable method.

A heavy duty switch and some over-rated power resistors would likely outlast
many replacement OEM miracle-in-a-box modules.

The parts, wire, a cover for the hole where the original removed module was,
and a Saturday afternoon would likely cover the cost investment.

I'm fairly certain that there are off-the-shelf variable speed modules that
would be an adequate replacement for an automotive blower motor application.

--
Cheers,
WB
..............


"jim beam" > wrote in message
...
>
> you don't need to know this stuff any more than you need to know the gas
> excitation voltage in a broken fluorescent tube. because you're not going
> to unpot the thing and replace the chip. because it's probably not the
> chip in the first place.
>
> not trying to be rude - just trying to get you focused on the relevant
> stuff - that the two options a
>
> 1. continue replacing the existing [under-rated, low tech] unit.
> 2. build and deploy a pwm unit instead.
>
> #1 is really not /that/ expensive, particularly if you factor in time,
> even if it is part of the bmw marketing susceptibility tax.
>
> #2 is a much better time investment - it certainly has a much better
> return than figuring out that the existing unit is not repairable later
> rather than sooner.
>
>
> --
> fact check required
>

In message
>,
" > writes
> Instead of just a simple
>fan motor, it's a fan that's variable speed, driven by a PWM
>signal.
If by PWM you mean pulse width modulation, then it would allow for
variable speed, but a DC motor is an inductive load and is not sensibly
controlled by such a system unless there is something in the circuit to
allow the peak voltage generated by the motor at pulse cut of to be
shunted to earth.
--
Clive

On Mar 23, 6:48*am, Clive > wrote:
> In message
> >,
> " > writes> Instead of just a simple
> >fan motor, it's a fan that's variable speed, driven by a PWM
> >signal.
>
> If by PWM you mean pulse width modulation, then it would allow for
> variable speed, but a DC motor is an inductive load and is not sensibly
> controlled by such a system unless there is something in the circuit to
> allow the peak voltage generated by the motor at pulse cut of to be
> shunted to earth.
> --
> Clive

That "something" could be as simple as a diode. PWM is
commonly used to vary the power to a motor. BMW, for
example, uses it on the aux fan motor of the X5. And I
would suspect that it's also used for the blower motor
because you wind up wasting a lot less power that way.
And every little bit of power saved adds up and effects MPG.

On Mar 22, 7:42*pm, "R. Mark Clayton" >
wrote:
> Have you got a link to these "common problems" you keep posting about?
>
> "Bimmer Owner" > wrote in message
>
> ...
>
> > 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....
>
> =========
>
>
>
> > Almost every BMW E39 (5-series) and E38 (7-series) and E46 (3-series)
> > has shorts that develop in the trunk wiring loom - all in the same spot!- Hide quoted text -
>
> - Show quoted text -

I don't have a link, but we had the blower resistor widget
go on an X5 here. And the aux cooling fan motor has gone
twice. There are plenty of threads online about many people having
those problems. Oh, and don't forget the
nice X5 feature where the cable that they use to hold up the
windows snaps, sending the window crashing down inside
the door, breaking it into a million pieces. Had that happen
twice too, once while the car was just sitting in the driveway.
Other time was driving down the highway.

Then there are their defective rubber parts. Like the boot on
the intake manifold that cracks in just a few years. Or the
CV joint boots. I've had lots of cars with CV boots and
only on the X5 do they fail every 20K miles. I've seen Honda CRVs
that went 200K miles with no failure.

In message
>,
" > writes
>That "something" could be as simple as a diode. PWM is
>commonly used to vary the power to a motor. BMW, for
>example, uses it on the aux fan motor of the X5. And I
>would suspect that it's also used for the blower motor
>because you wind up wasting a lot less power that way.
>And every little bit of power saved adds up and effects MPG.
I agree with all you say.
--
Clive

On 03/21/2013 08:08 PM, Scott Dorsey wrote:
> In article >, jim beam > wrote:
>> On 03/21/2013 07:23 PM, Nate Nagel wrote:
>>>
>>> *why* is it overheating?
>>
>> because it's linear, retard. if you don't know what they means, ****
>> off until you find out.
>
> Nothing wrong with linear motor control, it's just inefficient and
> produces a lot of heat. I used to work in a place with a 1.2 MW DC
> motor

that must have been interesting - what did that motor do?


> whose field coil voltage was controlled by a couple rooms full
> of cast-iron resistors.

that must have been a sight to see too.


> The resistance array lasted nearly 80 years
> before the whole facility was taken down.

shipped to china? or replaced by pwm controllers?


>
> As long as you keep within the safe operating area of the semiconductors,
> you're fine. If you exceed them, bad things happen. But we don't know
> if the semiconductors are failing on these things, or if it's just
> ordinary RoHS solder failures; the RoHS crap doesn't like thermal cycling
> so well.
> --scott
>


--
fact check required

On 03/23/2013 03:48 AM, Clive wrote:
> In message
> >,
> " > writes
>> Instead of just a simple
>> fan motor, it's a fan that's variable speed, driven by a PWM
>> signal.
> If by PWM you mean pulse width modulation, then it would allow for
> variable speed, but a DC motor is an inductive load and is not sensibly
> controlled by such a system unless there is something in the circuit to
> allow the peak voltage generated by the motor at pulse cut of to be
> shunted to earth.

ancient news - controller designers and semiconductor manufacturers have
been on top of this from day 1.


--
fact check required

On 03/23/2013 04:33 AM, wrote:
> On Mar 22, 7:42�pm, "R. Mark Clayton" >
> wrote:
>> Have you got a link to these "common problems" you keep posting about?
>>
>> "Bimmer Owner" > wrote in message
>>
>> ...
>>
>>> 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...
>>
>> =========
>>
>>
>>
>>> Almost every BMW E39 (5-series) and E38 (7-series) and E46 (3-series)
>>> has shorts that develop in the trunk wiring loom - all in the same spot!- Hide quoted text -
>>
>> - Show quoted text -
>
> I don't have a link, but we had the blower resistor widget
> go on an X5 here. And the aux cooling fan motor has gone
> twice. There are plenty of threads online about many people having
> those problems. Oh, and don't forget the
> nice X5 feature where the cable that they use to hold up the
> windows snaps, sending the window crashing down inside
> the door, breaking it into a million pieces. Had that happen
> twice too, once while the car was just sitting in the driveway.
> Other time was driving down the highway.
>
> Then there are their defective rubber parts. Like the boot on
> the intake manifold that cracks in just a few years. Or the
> CV joint boots. I've had lots of cars with CV boots and
> only on the X5 do they fail every 20K miles. I've seen Honda CRVs
> that went 200K miles with no failure.
>

serious question - why did you buy it?


--
fact check required

In message >, Bimmer Owner
> writes
>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.
Motors are not just a resistive load though.
--
Clive