On 03/25/2013 10:13 AM, Bimmer Owner wrote:
On Mon, 25 Mar 2013 12:26:52 -0400, clare wrote:

I'd wager it 'can' be done - it's just going to take an hour or so
to get the leads in place.
Bet I can do it in less than half an hour - without the MaxiTester
and in about 5 or 10 minutes with it.

I'd be very happy to see pictures of the test leads in situ
because I personally tried (and succeeded) in getting the 40
amp blower motor fuse F76 out and back in, but I wouldn't
want to do it more than once in my life.

From memory, here's what I did:
. I moved the passenger front seat as far back as I could
. I lowered the passenger front seat back as far back as it goes
. I removed the ignition key and disconnected the battery negative lead
. I removed the panel from the bottom of the glovebox
. I removed the Phillips screw and panel off to the passenger left kneecap
. I lay upside down on the flattened passenger seat, head in the footwell
. I located the general module III (GMIII)
. With my arms bent wildly arms over my head, I disconnected harness connectors
. The first enigmatic connector was the white connector X332
. The next diabolical connector was the small black X253
. And the last puzzling connector was the large black X254
. By now, I could slightly see the yellow 40 & red 50 amp fuses F76 & F77
. With a flathead 1/8" screwdriver, I lifted the yellow fuse F76 up & out
. That took about an hour or three.
. Putting the fuse back was even harder than removing it


as said by others, buy a clamp-on current meter. it's not like you'd
never use it again.


--
fact check required

On 03/25/2013 09:54 AM, Bimmer Owner wrote:
On Sat, 23 Mar 2013 07:20:44 -0700, jim beam wrote:

serious question - why did you buy it?

As for me, I fell sway to all the people saying how great the bimmer was.

It was only after I owned it, that I realized that BMW engineers knew
how to design a suspension and a drive train, but they had no idea
how to build a machine.

To their credit, some people say it's not the engineers fault as
they probably know by now that every single Bosch 5.7 ABS control
module fried in every one of the vehicles it was placed in, and that
the final stage unit cooked itself to death in every single BMW it
was ever placed in, and that the 2-bar plastic cooling system
sprang a leak on almost every single BMW ever built, etc.

honda use a "plastic cooling system". it's not infallible, but you can
get 15+ years out of the first one. there's no reason bmw couldn't
achieve the same - if they wanted to.



In fact, there's absolutely NO WAY BMW can't know about these
egregious engineering flaws. So, the common conclusion is that
their customers don't care - so why should they.

that is the catch - bmw target a certain type of buyer that typically
won't keep a car more than 3 years. after that, they don't care and bmw
can safely switch to "maximize parts sales/write off the old cars and
sell new ones" mode.

in europe, bmw have been aggressive leaders in "recycling" and spend a
lot of money advertising the fact. in practice however, it means that
they buy used cars back and have them scrapped, thereby keeping used
parts off the market - the mba's have done their math.



To me, it smacks of 3rd-grade engineering from BMW, so, that's why
I, for one, am amazed (being an owner myself), how sophomoric BMW
engineering really is.

it depends on perspective. i agree that some appear to be extremely
rudimentary, but that is contradicted by the fact that they spend a huge
amount of money on r&d, and have boatloads of phd's on staff. they were
also rescued by a bunch of mba's in the 70's and have had a root and
branch focus on design life ever since.



Disclaimer: Yet, the drive train is phenomenal!

call me when you have 100k miles on it...


--
fact check required

jim beam wrote:

On 03/24/2013 02:30 PM, Jamie wrote:

amdx wrote:

that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the
motor coils cause it to vibrate and make a humming noise at the pwm
control frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

I see many Motor Speed Control Manufacturers upped their PWM
frequency to be between 16 K to 22 K to eliminate much of the noise.
Mikek

Sure, if you don't mind heating the motor up...

Jamie


good point - how much? sure, big motor coils, big inductors -so how to
balance against pulse frequency for a bigger motor like a blower fan?

THe problem is eddy currents at high pulse rates. Between the wire
used and the core you can get heating in the motor..

Most inverters or pulsers for industrial drives tend to operate in the
8kHz range, that seems to be a good compromise.

Another way to do this, is to have an inductor on board with the
speed control circuit. You would PWM that inductor in series to a filter cap
on the output which will then give you a clean variable DC. THe inductor
will be doing all variable voltages. This is a form of a PFC type of
supply and the only heat you get is from the DC coil R in the inductor
and the heat from the switching MOSFET, which should both be rather
low. BY doing it this way, you could operate a switcher at lets say up
in the 100kHz or more range and this would keep the size of the caps and
inductor small.

It is cheaper to use the motor as the inductor for PWM control but,
it also can radiate noise on the lead wires. I guess one could actually
mount the speed control directly on the motor using PWM and the noise
problem should be minimum.

Calculating the cost between the two, BMW most likely decided to go
with the basic linear type, Because why should they care? It'll most
likely make it past it's warranty!

Jamie

On Mon, 25 Mar 2013 17:34:25 -0700, jim beam wrote:

buy a clamp-on current meter

I have a Fluke 75, so I'll have to see what clamp on DC current
probes fit it.

On Mon, 25 Mar 2013 14:55:02 -0400, Scott Dorsey wrote:

Okay, notice on the lefthand photo, there are two sets of three solder joints
on the lefthand side of the board, which show signs of recent rework. There
are TO-220 transistors attached to them, which are behind the board and you
cannot see.

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Like a good detective, you've seen something that I had not seen.
What you said makes sense. However, I have never heard of anyone
removing two transistors from that board. I wonder if those two
sets of inline pins are just the connections to the heat sink?

Since I have an FSU in my possession, I will try to lift the board.
The FSU that I have, DOES have two sets of these "spikes" sticking up
at those very locations, so, clearly "something" is there.
http://www2.picturepush.com/photo/a/...g/12511535.jpg

But, what puzzles me is that nobody has ever mentioned removing
transistors from those two spots. Therefore, I suspect they're just
anchor posts, since the solder is clearly removed in the autopsies.

On Mon, 25 Mar 2013 18:12:53 -0400, tm wrote:

Yes, what Scott said. Where are the two transistors that were soldered in
the pair of three holes on the right of the right photo.

I always thought those were just "posts" tying the circuit board
to something inside the FSU - but I do agree that all the FSU
autopsies show those posts being unsoldered to remove the board.

Here's the quote that came with this picture, for example:
http://www4.picturepush.com/photo/a/...g/12511542.jpg

"Bimmer Owner" wrote in message
...
On Mon, 25 Mar 2013 14:55:02 -0400, Scott Dorsey wrote:

Okay, notice on the lefthand photo, there are two sets of three solder
joints
on the lefthand side of the board, which show signs of recent rework.
There
are TO-220 transistors attached to them, which are behind the board and
you
cannot see.

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Like a good detective, you've seen something that I had not seen.
What you said makes sense. However, I have never heard of anyone
removing two transistors from that board. I wonder if those two
sets of inline pins are just the connections to the heat sink?

Since I have an FSU in my possession, I will try to lift the board.
The FSU that I have, DOES have two sets of these "spikes" sticking up
at those very locations, so, clearly "something" is there.
http://www2.picturepush.com/photo/a/...g/12511535.jpg

But, what puzzles me is that nobody has ever mentioned removing
transistors from those two spots. Therefore, I suspect they're just
anchor posts, since the solder is clearly removed in the autopsies.

No, they are two TO-220 cased transistors. they are most likely attached to
the heat sink somehow. Like was mentioned before, finding out the part
numbers on those transistors will reveal a lot.

tm

On Tue, 26 Mar 2013 04:22:30 +0000, Bimmer Owner wrote:

But, what puzzles me is that nobody has ever mentioned removing
transistors from those two spots. Therefore, I suspect they're just
anchor posts, since the solder is clearly removed in the autopsies.

There is something critical about those two sets of inline posts
because, as I dig deeper, I see others concentrated on them also.

For example, the quote below came with the picture below:
http://www1.picturepush.com/photo/a/...g/12511554.jpg

On 03/25/2013 08:56 PM, Bimmer Owner wrote:
On Mon, 25 Mar 2013 17:34:25 -0700, jim beam wrote:

buy a clamp-on current meter

I have a Fluke 75, so I'll have to see what clamp on DC current
probes fit it.


cheaper to buy a whole new meter!

or google for this guy:
"ESI 695 80 Amps DC/AC Low Current Probe"


--
fact check required

On Tue, 26 Mar 2013 04:22:30 +0000, Bimmer Owner wrote:

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Looking more deeply, I find ANOTHER reference to the two MOSFETS,
which, are clearly the two transistors shown in the wiring diagram
that you had surmised must exist (by detective work).

Here's another quote which went along with this photo below
that mentions the unknown-as-yet MOSFETS:
http://www3.picturepush.com/photo/a/...g/12511566.jpg

On 03/25/2013 09:40 PM, Bimmer Owner wrote:
On Tue, 26 Mar 2013 04:22:30 +0000, Bimmer Owner wrote:

But, what puzzles me is that nobody has ever mentioned removing
transistors from those two spots. Therefore, I suspect they're just
anchor posts, since the solder is clearly removed in the autopsies.

There is something critical about those two sets of inline posts
because, as I dig deeper, I see others concentrated on them also.

For example, the quote below came with the picture below:
http://www1.picturepush.com/photo/a/...g/12511554.jpg

Quote:

Originally Posted by olivier577 After soldering the lost/refound component, remaking the joints of the 2 mosfet and testing the FSU alone with an oscilloscope, here are my observations: - the FSU works again - there is no PWM , the gates signals are continuous voltage only , this is the reason why it heat so much its aluminium box... In fact there is no point on the board where square signals are present. Can somebody check its own FSU if it's the same ? - the 2 bridges are in fact 2 resistors 10 milliohm used to balance the currents between the 2 MOSFET and balance the power also. The mesure of the DC voltage on those resistors can be used to evaluate the current of the blower and its worn state. - I guess the principal duty of the computer on the other side is switching off the power transistors if the control voltage goes under 1V. I put the FSU back in the car and it still work, I don't know if it will last long. because of the heat... Olivier

"sophomoric" indeed.


--
fact check required

On Mon, 25 Mar 2013 21:42:16 -0700, jim beam wrote:

or google for this guy:
"ESI 695 80 Amps DC/AC Low Current Probe"

This seems to only be $107 but it doesn't say whether it works
with the Fluke 75 or not.
http://www.amazon.com/ESI-695-Amps-C.../dp/B000FN4IUK

On Tue, 26 Mar 2013 00:39:23 -0400, tm wrote:

they are two TO-220 cased transistors.
finding out the part numbers on those transistors will reveal a lot.

I have an FSU in my possession, so I will dig them out & snap
a photo when done and post back the results.

To my knowledge, nobody has ever posted a photo of what those
two MOSFETS look like, nor the part number.

The mesure of the DC voltage on those resistors can be used to
evaluate the current of the blower and its worn state.

What does this sentence above mean?

Does it intimate the blower motor is actually drawing more
current as it ages (as someone had suggested prior)?

On Tue, 26 Mar 2013 04:58:48 +0000, Bimmer Owner wrote:

This seems to only be $107 but it doesn't say whether it works
with the Fluke 75 or not.
http://www.amazon.com/ESI-695-Amps-C.../dp/B000FN4IUK

For the same price, it looks like we can get a separate unit:
http://www.westsidewholesale.com/gif...ke-t5-600.html

Fluke T5-600, SKU: 133038, $109.95

On 03/25/2013 10:02 PM, Bimmer Owner wrote:
The mesure of the DC voltage on those resistors can be used to
evaluate the current of the blower and its worn state.

What does this sentence above mean?

with two resistors in series, the voltage across any one is a function
of its resistance and the current in the current in the other.



Does it intimate the blower motor is actually drawing more
current as it ages (as someone had suggested prior)?

good question - there might be a slight change in draw as the motor
ages, but unless the motor has serious bearing health issues or blows a
magnet coil, i can't imagine it will change by much. and other than
short circuit detection/protection, i have doubts about the extent to
which such a simple controller will need to know.


--
fact check required

"Bimmer Owner" wrote in message
...
On Tue, 26 Mar 2013 04:22:30 +0000, Bimmer Owner wrote:

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Looking more deeply, I find ANOTHER reference to the two MOSFETS,
which, are clearly the two transistors shown in the wiring diagram
that you had surmised must exist (by detective work).

Here's another quote which went along with this photo below
that mentions the unknown-as-yet MOSFETS:
http://www3.picturepush.com/photo/a/...g/12511566.jpg

Quote:

Originally Posted by olivier577 The 2 MOSFET drain and source are tied together but the gates are differents On the picture , one of the component is gone with the rubber foam : its look like transistor : black with 3 pins ( it 's not bipolar transistors ). It happen to me also : the component gone so easily that I didn't realize it, maybe it is the issue for that FSU. It is only while I compare to other pictures in the forum that there was a lack of component on my board. fortunately I found it together with the rubber foam parts, so I will solder it back later

As a general rule, MOSFETs are not used for linear current control. It is
more looking like this is a switcher (PWM) though I dont see an inductor.
Could be they just use the motor for that.

If you can see any numbers on the devices, it will help. Also, the solder
sure looks like RoHS **** tin.

wrote:

Maybe it's time to look at this thing like gas and brakes...
You put gas in, you go so far. You put one of these
blower modules in and you go for a few years again.
It's not like they are a $500 or $1000 puter. Don't they
cost like $50? I mean how much is time worth trying
to reverse engineer it.....

This is how people are. At some point intellectual curiosity takes over.

In this case it might actually be worth it, because of the sheer number of
the things out there that are failing.... one person figuring the failure
mode out might save a lot of people that grief.

But mostly it's just intellectual curiosity.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article , jim beam wrote:
On 03/25/2013 05:57 PM, Jamie wrote:
jim beam wrote:

Another way to do this, is to have an inductor on board with the
speed control circuit. You would PWM that inductor in series to a filter
cap
on the output which will then give you a clean variable DC. THe inductor
will be doing all variable voltages.

ok, as i understand it, and as i said to scott earlier, this is a
problem because it mungs low speed motor start and low speed torque.

Not really, it's feeding the motor with variable DC from that integrator
stage. It's not much different than a big rheostat in terms of starting
torque. It's just more expensive and less reliable and quieter.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Bimmer Owner wrote:
On Mon, 25 Mar 2013 17:34:25 -0700, jim beam wrote:

buy a clamp-on current meter

I have a Fluke 75, so I'll have to see what clamp on DC current
probes fit it.

I don't think Fluke makes much in the way of current probes for DC with
appreciable sensitivity. The i1010 is sensitive enough for this sort of
job, but not for a lot of other things you might want. They do make some
fancy intelligent probes but they're all more expensive than just buying
a Fluke clamp meter like the 365.

That said, I have a cheapo Extech 380947 and it's not built like the Fluke
but it's sensitive enough to detect small ground leakage currents.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Bimmer Owner wrote:
On Mon, 25 Mar 2013 14:55:02 -0400, Scott Dorsey wrote:

Okay, notice on the lefthand photo, there are two sets of three solder joints
on the lefthand side of the board, which show signs of recent rework. There
are TO-220 transistors attached to them, which are behind the board and you
cannot see.

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Like a good detective, you've seen something that I had not seen.
What you said makes sense. However, I have never heard of anyone
removing two transistors from that board. I wonder if those two
sets of inline pins are just the connections to the heat sink?

No, there are two transistors bolted to the heat sink. That's why the heat
sink is there, to cool those two power transistors.

But, what puzzles me is that nobody has ever mentioned removing
transistors from those two spots. Therefore, I suspect they're just
anchor posts, since the solder is clearly removed in the autopsies.

No, the spacing is consistent with a TO-220 transistor pair, and if it's
a linear pass regulator like it appears to be, there needs to be a big
transistor somewhere. Also, of course, there is the heatsink.

That IC is only control logic, it just takes some mystery input signal and
produces a variable voltage for the transistor base. Those two transistors
are doing all the hard work. BUT, if you want to replace the device with
a retrofit one, you need to know what that mysterious input signal is.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

tm wrote:


As a general rule, MOSFETs are not used for linear current control. It is
more looking like this is a switcher (PWM) though I dont see an inductor.
Could be they just use the motor for that.

It's not a switcher. And those transistors may not be MOSFETs. But there
is no reason not to use mosfets in linear mode, other than the fact that
no two off the line have the same gain or transconductance.

If you can see any numbers on the devices, it will help. Also, the solder
sure looks like RoHS **** tin.

Agreed.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 03/26/2013 05:58 AM, Scott Dorsey wrote:
In article , jim beam wrote:
On 03/25/2013 05:57 PM, Jamie wrote:
jim beam wrote:

Another way to do this, is to have an inductor on board with the
speed control circuit. You would PWM that inductor in series to a filter
cap
on the output which will then give you a clean variable DC. THe inductor
will be doing all variable voltages.

ok, as i understand it, and as i said to scott earlier, this is a
problem because it mungs low speed motor start and low speed torque.

Not really, it's feeding the motor with variable DC from that integrator
stage.

i understand that - and variable voltage is the problem. the secondary
[bordering on primary in some applications] advantage of pwm is low
speed start and torque. if a motor starts at low dc voltage, not only
is the start speed inconsistent, it has little torque. pwm can start a
motor slower and at much higher torque. it's a big deal.


It's not much different than a big rheostat in terms of starting
torque. It's just more expensive and less reliable and quieter.
--scott



--
fact check required

On 03/26/2013 06:07 AM, Scott Dorsey wrote:
Bimmer Owner wrote:
On Mon, 25 Mar 2013 17:34:25 -0700, jim beam wrote:

buy a clamp-on current meter

I have a Fluke 75, so I'll have to see what clamp on DC current
probes fit it.

I don't think Fluke makes much in the way of current probes for DC with
appreciable sensitivity. The i1010 is sensitive enough for this sort of
job, but not for a lot of other things you might want. They do make some
fancy intelligent probes but they're all more expensive

way to understate - those things are insanely expensive. otoh, there's
almost no competing product, so they have the ability to leverage pricing.

http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=614-1090-ND

that's why i settled for the esi unit. not as good as the fluke, but
has similar sensitivity in a package robust enough for automotive use.


than just buying
a Fluke clamp meter like the 365.

That said, I have a cheapo Extech 380947 and it's not built like the Fluke
but it's sensitive enough to detect small ground leakage currents.
--scott



--
fact check required

On 03/25/2013 10:06 PM, Bimmer Owner wrote:
On Tue, 26 Mar 2013 04:58:48 +0000, Bimmer Owner wrote:

This seems to only be $107 but it doesn't say whether it works
with the Fluke 75 or not.
http://www.amazon.com/ESI-695-Amps-C.../dp/B000FN4IUK

For the same price, it looks like we can get a separate unit:
http://www.westsidewholesale.com/gif...ke-t5-600.html

Fluke T5-600, SKU: 133038, $109.95


if you want your purchase to be useful for automotive, you want
sensitivity. and ability to hook it up to a scope is a huge plus.


--
fact check required

On 03/25/2013 11:06 PM, tm wrote:

"Bimmer Owner" wrote in message
...
On Tue, 26 Mar 2013 04:22:30 +0000, Bimmer Owner wrote:

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Looking more deeply, I find ANOTHER reference to the two MOSFETS,
which, are clearly the two transistors shown in the wiring diagram
that you had surmised must exist (by detective work).

Here's another quote which went along with this photo below
that mentions the unknown-as-yet MOSFETS:
http://www3.picturepush.com/photo/a/...g/12511566.jpg

Quote:

Originally Posted by olivier577 The 2 MOSFET drain and source are tied together but the gates are differents On the picture , one of the component is gone with the rubber foam : its look like transistor : black with 3 pins ( it 's not bipolar transistors ). It happen to me also : the component gone so easily that I didn't realize it, maybe it is the issue for that FSU. It is only while I compare to other pictures in the forum that there was a lack of component on my board. fortunately I found it together with the rubber foam parts, so I will solder it back later

As a general rule, MOSFETs are not used for linear current control. It
is more looking like this is a switcher (PWM)

there's been another post - the output has been scoped. it's linear.

besides, to-220 isn't reserved for fet's.

http://www.digikey.com/product-detail/en/BUV26G/BUV26GOS-ND/1476296
http://www.digikey.com/product-detail/en/MBR1545CT-E3%2F45/MBR1545CT-E3%2F45GI-ND/2153184


though I dont see an
inductor. Could be they just use the motor for that.

now you're guessing.



If you can see any numbers on the devices, it will help. Also, the
solder sure looks like RoHS **** tin.

you're not telling the difference from a simple visual. sorry.


--
fact check required

On Mar 26, 9:10*am, (Scott Dorsey) wrote:
Bimmer Owner wrote:

On Mon, 25 Mar 2013 14:55:02 -0400, Scott Dorsey wrote:

Okay, notice on the lefthand photo, there are two sets of three solder joints
on the lefthand side of the board, which show signs of recent rework. *There
are TO-220 transistors attached to them, which are behind the board and you
cannot see.

Ah, I see what you're talking about and I've circled them in this photo:
http://www3.picturepush.com/photo/a/...g/12511526.jpg

Like a good detective, you've seen something that I had not seen.
What you said makes sense. However, I have never heard of anyone
removing two transistors from that board. I wonder if those two
sets of inline pins are just the connections to the heat sink?

No, there are two transistors bolted to the heat sink. *That's why the heat
sink is there, to cool those two power transistors.

But, what puzzles me is that nobody has ever mentioned removing
transistors from those two spots. Therefore, I suspect they're just
anchor posts, since the solder is clearly removed in the autopsies.

No, the spacing is consistent with a TO-220 transistor pair, and if it's
a linear pass regulator like it appears to be, there needs to be a big
transistor somewhere. *Also, of course, there is the heatsink.

That IC is only control logic, it just takes some mystery input signal and
produces a variable voltage for the transistor base. *Those two transistors
are doing all the hard work. *BUT, if you want to replace the device with
a retrofit one, you need to know what that mysterious input signal is.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

One key question in all this is if the interface from car to
"resistor block" is some kind of simple digital interface,
ie it sends some bits that get interpreted as "go to speed 3"
or does it send a PWM signal. My guess is the latter.
That's my understanding of what BMW does with the aux
radiator fan in the X5. Another German electronic miracle
that fails and in doing so, mysteriously drains the battery.

Someone should put an oscilloscope on this and find
out what the signal looks like. If it sends a digital code,
then making a replacement from scratch is a big
hurdle. If it's sending a PWM signal, they you could
build an equivalent from Radio Shack parts. It still
seems like more work than it's worth.

How fast are these things failing for those that want
to make their own? 2002 X5 here and it's only had this
problem once, about 2 years ago and replacement one
is still working. And another data point. The failure on
that X5 resulted in the blower draining the battery when
the car was off. Blower ran fine. Only odd thing in
retrospect was that when the car was off, a couple times
I heard a faint noise. In retrospect, it was probably
the blower getting just enough current to start to turn
then stop. And only noticed it a couple times. The
bad thing with the failure mode of this and the AC fan
is that both were draining the battery and both were
very hard to pinpoint, resulting in huge labor charges.

On Tue, 26 Mar 2013 05:00:41 +0000, Bimmer Owner wrote:

To my knowledge, nobody has ever posted a photo of what those
two MOSFETS look like, nor the part number.

The semi-conductors circled are not the MOSFET you are looking for
information on. The Mosfet is 14 pin and what is circled is something
different.

I think if these Mosfets were in 1000 BMW owner's hands, maybe one person
out of 1000, if that, would have the skills to install in the carcass we
have left after removing all the potting material. How are we determining
the MOSFET is bad in any situation? Again, even with a data sheet which
we will never get because these Mosfets are supposedly "special" to BMW
(just like they try to hide their MAF sensor). Few would have the skills
to test a 14 pin Mosfet. I believe the FSUs that have been "repaired" are
again the usual "open" circuit BMW seems to like so much (can we say ABS
module).

On Mon, 25 Mar 2013 22:23:22 -0700, jim beam wrote:

The mesure of the DC voltage on those resistors can be used to
evaluate the current of the blower and its worn state.

What does this sentence above mean?

with two resistors in series, the voltage across any one is a function
of its resistance and the current in the current in the other.

Ah, so it's a plain old voltage divider?

On Tue, 26 Mar 2013 09:10:56 -0400, Scott Dorsey wrote:

BUT, if you want to replace the device with a retrofit one, you need to
know what that mysterious input signal is.

All I know of the HVAC input signal is that it's a 2.0 to 7.8 VDC
signal from the HVAC controller, presumably to correspond to the
various levels of the fan blower motor speed.

On Tue, 26 Mar 2013 07:37:09 -0700, wrote:

One key question in all this is if the interface from car to "resistor
block" is some kind of simple digital interface, ie it sends some bits
that get interpreted as "go to speed 3" or does it send a PWM signal.

All I know is that the HVAC controller sends a 2.0 VDC to 7.8 VDC signal
to one of the five pins of the FSU. I presume that directly corresponds
to the desired blower motor speed - but that is conjecture on my part.

How fast are these things failing for those that want to make their own?

The originals fail within about 5 years. I've had my second one fail in
3 years. I think we can safely say about 3 to 5 years is the lifecycle
but nobody really knows for sure (least of all me).


The failure on that X5 resulted in the blower draining the battery
when the car was off. Blower ran fine. Only odd thing in retrospect
was that when the car was off, a couple times I heard a faint noise.

This is one of the classic failure indications! Very very very common!
However, another classic failure indication, other than the dead
battery in the morning, is a blower that has a "mind of its own".

Together, those two sets of symptoms account for 99% of the failures.

Of all the anecdotal evidence presented, I don't think I've ever heard
of a failure being that the system was totally dead.

What that tells us, I don't know.

On Tue, 26 Mar 2013 08:56:22 -0400, Scott Dorsey wrote:

one person figuring the failure mode out might save a
lot of people that grief.

But mostly it's just intellectual curiosity.

Exactly!

"Bimmer Owner" wrote in message
...
On Tue, 26 Mar 2013 09:10:56 -0400, Scott Dorsey wrote:

BUT, if you want to replace the device with a retrofit one, you need to
know what that mysterious input signal is.

All I know of the HVAC input signal is that it's a 2.0 to 7.8 VDC
signal from the HVAC controller, presumably to correspond to the
various levels of the fan blower motor speed.


But is that a clean DC level or a pulse width modulated signal? If it was
measured with a multimeter, you won't know.

Has anyone probed around the module with a scope? Is that possible?

That and the question about the TO-220 devices. I think it would be possible
to make a better replacement if those questions were answered.

tm

wrote:

One key question in all this is if the interface from car to "resistor
block" is some kind of simple digital interface, ie it sends some bits
that get interpreted as "go to speed 3"
or does it send a PWM signal.

Your idea about testing it is correct, however a bad one can work fine
until it gets hot enough for the IC chip to fail. Hvac control voltage is
0-8 VDC.

The load resistor should have a metal case mounted on a heatsink to
dissipate the heat if you are going to run the test more than a few
minutes.

My original 13 spike FSU was replaced twice under warranty, so the car
had 3 FSU's. When the 3rd old style failed i replaced it with the new
design FSU. That was 8-9 years ago, it is still working. One thing not
considered in your post is how many did not use OEM units, the $75 eBay
ones are junk. The $175 units at the stealer seem to hold up a little
better.

Scott Dorsey wrote:

wrote:
It's not like they are a $500 or $1000 puter. Don't they cost like $50?
I mean how much is time worth trying to reverse engineer it.....

Bear in mind that the $75 Sitronic Ebay FSU is known to be even
more faulty than the $175 Valeo FSU from the stealer.

I can think of nice test equipment to buy instead of a $175 FSU every
few years!

"Bimmer Owner" wrote in message
...
On Tue, 26 Mar 2013 08:56:22 -0400, Scott Dorsey wrote:

one person figuring the failure mode out might save a
lot of people that grief.

But mostly it's just intellectual curiosity.

Exactly!


I don't even own a BMW. After this thread, I don't think I ever will.

On Tue, 26 Mar 2013 15:30:41 +0000, Bimmer Owner wrote:

All I know of the HVAC input signal is that it's a 2.0 to 7.8 VDC signal
from the HVAC controller, presumably to correspond to the various levels
of the fan blower motor speed.

Here is a picture of the BMW E39 HVAC/IHKA controller and sampling fan.
http://www4.picturepush.com/photo/a/...g/12514687.jpg

I'm googling for specs as we speak.

On Mar 26, 11:53*am, "tm" wrote:
"Bimmer Owner" wrote in message

...

On Tue, 26 Mar 2013 09:10:56 -0400, Scott Dorsey wrote:

BUT, if you want to replace the device with a retrofit one, you need to
know what that mysterious input signal is.

All I know of the HVAC input signal is that it's a 2.0 to 7.8 VDC
signal from the HVAC controller, presumably to correspond to the
various levels of the fan blower motor speed.

But is that a clean DC level or a pulse width modulated signal? If it was
measured with a multimeter, you won't know.

The other possibility is that it's a digital command signal of
some kind. I don't know how they typically do that, but if a
0 is 0 volts and a 1 is 12V, for example, looking at it with a
volt meter, you would see a range like that given.
They do have that 16 pin chip there, doing something.
It might receive the command and then output the appropriate
PWM for rest of the circuit.




Has anyone probed around the module with a scope? Is that possible?

That and the question about the TO-220 devices. I think it would be possible
to make a better replacement if those questions were answered.

tm

"Scott Dorsey" wrote in message
...
Bimmer Owner wrote:
On Mon, 25 Mar 2013 17:34:25 -0700, jim beam wrote:

buy a clamp-on current meter

I have a Fluke 75, so I'll have to see what clamp on DC current
probes fit it.

I don't think Fluke makes much in the way of current probes for DC with
appreciable sensitivity. The i1010 is sensitive enough for this sort of
job, but not for a lot of other things you might want. They do make some
fancy intelligent probes but they're all more expensive than just buying
a Fluke clamp meter like the 365.

That said, I have a cheapo Extech 380947 and it's not built like the Fluke
but it's sensitive enough to detect small ground leakage currents.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I agree that the Extech meters are a good buy for the money. I have the
380947 (400 amp) and the 380942 (30 amp + voltmeter).

They are really handy to have in the toolbag.


tm

jim beam wrote:

if it's just a two-layer board, maybe. assuming you get the specs on
the chips of course. but you'll need more than two units and a whole
lot of patience trying to reverse the schematic if it's 4 or more
layers. and you still don't achieve anything more than having a broken
light bulb in your hand.

what you need to do is get the operational capacities of the /working/
unit, and work with those. that the unit is a black box is completely
irrelevant.


Yawn. I worked with 16 layer boards at a factory troubleshooting
defective, new boards that cost over $8,000 to stuff. The internal
routing of a simple low frequency board is irrelevant for drawing a
schematic. You can X-ray a board or mill it one layer at a time if you
want to duplicate the routing. All you need to do for bais reverse
engineering is to trace each with an ohm meter by probing every pad and
termination to identify the signal path and draw a schematic from your
notes. I've done this with four layer boards for 30+ years. "Specs on
the chips" makes things easier but knowing who made it, and how it's
connected will tell you if it is a custom part or just house numbered.

There are industrial solvents to remove any potting compound, but
they aren't cheap or easy to buy. Failure analysis is a specialty in
electronics manufacturing. It is expensive but gives you the answers
you need so you can design out the problems.


A jig to hold the module in a CNC machine would allow you to cut
accurate holes down to the right points to see if the IC was bad,
without unpotting a failed unit. Then a test fixture with 'Pogo Pins'
would allow you to see what was bad. If there were enough bad units, it
would be worth designing and programming a computerized fixture.

--

Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

Sometimes Friday is just the fifth Monday of the week.