Root cause insight into the common BMW blower motor resistor failures

Page 11 of 14  
On Tue, 26 Mar 2013 15:51:52 -0400, tm wrote:

The red jumper was a hack added by one user to fix the solder cracks, I think.
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I am aware of that. It looks like it ties the two collectors together. But does it go to the contact that connects to the fuse? The main point is "do the collectors (center pin on transistor) connect to the 12 volt input to the module"?
Thanks, tm
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On Tue, 26 Mar 2013 15:51:52 -0400, tm wrote:

This implies two transistors (although I only found one).
I will dig through the mess again - but I think I was too fat thumbed when I cut it open, and may have destroyed the evidence.
I do have a second FSU (since two failed on me) though ... but I want to try to FIX that one (instead of destroying it).
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On 03/28/2013 06:21 AM, Bimmer Owner wrote:

dude, give up on that already. you'll never get good thermal contact second time around.
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You said you tested the FSU alone. If so, how can you say there is no PWM signal between the car and FSU?
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 ?

DC voltage on those resistors can be used to evaluate the current of the bl ower and its worn state.
Say what? 10 milliohms is .01 ohms. How could that possibly balance the power to a motor in a 40 amp circuit?

Which makes no sense at all.

It seems they last at least a few years. Maybe it's like gas. You buy it and you go so far. I think you're in way over your head here;
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/You said you tested the FSU alone. If so, how can you /say there is no PWM signal between the car and FSU?
/ 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 ?

/Say what? 10 milliohms is .01 ohms. How could that /possibly balance the power to a motor in a 40 amp circuit?
Not to the motor idiot. To the transistors.

/Which makes no sense at all.
Certainly not to you.

/It seems they last at least a few years. Maybe it's like /gas. You buy it and you go so far. I think you're in way /over your head here;
But not yours?
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No, because I'm not the one trying to reverse engineer an electronics module in a car, that contains among other things, an unknown 16 pin chip, without benefit of any of the necessary tools. You guys don't even know what the interface to the car is, whether it's analog or digital, etc. And you don't even have an oscilloscope to look at anything with.
Oh, BTW, if you're all so smart, how come I was the first one to find out for you that the 16 pin chip number you had is a vaild one for a real chip?
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snipped-for-privacy@optonline.net wrote:

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.

Resistors are used in the emitter path when combining two or more to the same circuit. This is needed to insure both transistors share in the load when it comes to biasing... Otherwise, you'll get one that favors beta and the other will sit back and snooze. Call it a ballast R if you wish.. These R values are generally low.
Jamie
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On Tue, 26 Mar 2013 14:09:11 -0400, Michael A. Terrell wrote:

It might be, but this Russian site intimates it's a temperature compensated voltage controller. http://tinyurl.com/crg2sms http://kazus.ru/schematics/electrical-engineering/search/go/?text=%D0%C5%C3%D3%CB%DF%D2%CE%D0%20ELMOS%2010901D&nohistory=1&h=1 http://monitor.espec.ws/section27/topic189041.html http://item.taobao.com/item.htm?id 918440884
Translation below: REGULATOR ELMOS 10901D Found: 100 Showing: 1 - 10 Car Voltage Regulator Category: Car Source: Radioland country Electronics Temperature controller cabin air KAMAZ Category: Car Source: Plans radiokonstruktsy Simple Temperature compensated voltage regulator. Controller together with thyristor-transistor electronic ignition unit with a long spark, ensuring the rapid start-ups at various operating conditions, allowed to increase battery life of up to nine years. Category: Car Source: For the life of a soldering iron ... Regulator for automotive windshield Category: Car Source: MASTER KIT The controller measures the wiper-this control is designed to use regular mode switch blades and is contactless. Category: Car Source: For the life of a soldering iron ... Temperature compensated voltage regulator device in some ways superior designs. The controller can be used as a universal device is suitable not only for mounting on any car, but everywhere, where the generator rotor speed is variable (eg, wind power). Choose the appropriate control elements, it can be easily adapted to work with any voltage (up to 400V) and excitation current (tens of amperes). Category: Car Source: For the life of a soldering iron ... Voltage regulator 2012.3702, 22.3702, 221.3702 Category: Car Source: For the life of a soldering iron ... Voltage regulator 201.3702 Category: Car Source: For the life of a soldering iron ... Voltage Regulator 13.3702 Category: Car Source: For the life of a soldering iron ... Voltage regulator RR132A, 1112.3702 Category: Car Source: For the life of a soldering iron ...
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Bimmer Owner wrote:

Be careful with so called information from those types of sites. Most of their information is badly translated, or just plain wrong. Tabao.com is a prime example of crap information. I have never found correct information there. Most is from chinese Ebay sellers who make things up about items they sell. They have no idea what it is, just that they can sell it on Ebay or Tabao.com.

thyristor-transistor electronic ignition unit with a long spark, ensuring the rapid start-ups at various operating conditions, allowed to increase battery life of up to nine years.

designs. The controller can be used as a universal device is suitable not only for mounting on any car, but everywhere, where the generator rotor speed is variable (eg, wind power). Choose the appropriate control elements, it can be easily adapted to work with any voltage (up to 400V) and excitation current (tens of amperes).

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

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:

[QUOTE=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[/QUOTE]
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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 shit tin.
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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.

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

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

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

now you're guessing.

you're not telling the difference from a simple visual. sorry.
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No, there are two transistors bolted to the heat sink. That's why the heat sink is there, to cool those two power transistors.

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."

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On Mar 26, 9:10 am, snipped-for-privacy@panix.com (Scott Dorsey) 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. 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.
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On Tue, 26 Mar 2013 07:37:09 -0700, snipped-for-privacy@optonline.net wrote:

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.

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).

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.
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snipped-for-privacy@optonline.net wrote:

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