Root cause insight into the common BMW blower motor resistor failures

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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.

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On Tue, 26 Mar 2013 09:43:58 -0700, snipped-for-privacy@optonline.net wrote:

Someone had scoped the whole board, and it was DC voltage everywhere (according to that reference). It's pretty clear there is no PWM.
The 16-pin surface mount chip seems to be a automotive temperature compensated voltage regulator with a huge voltage range, according to a lookup of the part number on it.
Here is the Elmos 10901D chip of my FSU as I cut it open today.
I wish there was a way to get rid of that heavy fibrous plastic goop! (What is that black fibrous tough stuff anyway?)
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wrote:

Are those the two transistors sitting on top?
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On Tue, 26 Mar 2013 15:04:51 -0400, tm wrote:

Actually, it's the same transistor, which broke in half while I was attempting to get the black rubber eraser stuff off of it to read the numbers.
It's really going to be HARD to read those numbers now...

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Okay, there is a TO-220 package that is split open there, with the backplate on the right and the cover on the left. Can you chip off enough of the araldite from the cover to be able to read the numbers on it?
Or, could you get a good picture of the die which is left on the piece on the right? We might be able to identify it with a sharp photo of the die... although from what I can see from the fuzzy photo it does not look like a very happy die.
If it is actually a MOSFET it will look like this:
http://www.panix.com/~kludge/fet1.jpg
(That's a package that is a little bigger than the TO-220, but you can still see the channel down the middle of the FET and the overheating damage to the source.... the three leads have been torn off in the unpotting process though.) --scott
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On Wed, 27 Mar 2013 09:16:55 -0400, Scott Dorsey wrote:

I will try this morning. (I was away on a trip for the past two days).
PS: Had to look up araldite: http://en.wikipedia.org/wiki/Araldite
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It's an epoxy resin filled with silica. It will come off with DMSO at three atmospheres or so. Sometimes a soak in DMSO for a couple weeks will make it peel off. This will also soften the PC board though. --scott
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"Bimmer Owner" wrote in message wrote:

Someone had scoped the whole board, and it was DC voltage everywhere (according to that reference). It's pretty clear there is no PWM.
The 16-pin surface mount chip seems to be a automotive temperature compensated voltage regulator with a huge voltage range, according to a lookup of the part number on it.
Here is the Elmos 10901D chip of my FSU as I cut it open today.

I wish there was a way to get rid of that heavy fibrous plastic goop! (What is that black fibrous tough stuff anyway?)
I have had good luck removing the stuff used on motorcycle voltage regulators that were potted soaking in MEK Methyl ethyl ketone (spelling?). Potent stuff. Use outdoors and keep your hands out of it. WW
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I don't know what it actually is but at work we desolved a potted firing system for a boat motor with something called OCP. Really stinks. Don't think I would want it in a car after it was used.
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On 2/4/2014 8:09 PM, Ralph Mowery wrote:

Chopper of Bend, Oregon. Now defunked. We used two-part black epoxy that took 24 hours to completely cure. When applied it was water thin. Had to prep the box with RTV to keep the potting from running out around the connectors.
Paul
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On Tue, 26 Mar 2013 15:30:41 +0000, Bimmer Owner wrote:

Here is a picture of the BMW E39 HVAC/IHKA controller and sampling fan.

I'm googling for specs as we speak.
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Well, that's about what you need to know. Game over. --scott
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On Thu, 21 Mar 2013 22:54:59 +0000 (UTC), Bimmer Owner

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.
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On Mar 21, 8:08 pm, snipped-for-privacy@snyder.on.ca wrote:

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.
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On 03/21/2013 05:08 PM, snipped-for-privacy@snyder.on.ca wrote:

indeed.
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On Thu, 21 Mar 2013 22:54:59 +0000 (UTC), Bimmer Owner

Hmm, it did look like it had quite a heat sink. I had assumed it used PWM to change speed, which should not generate much heat but my assumption might be wrong (or my understanding of PWM...) A solid state design that gets hot on purpose seems like a poor design to me.
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Bimmer Owner wrote:

It should generate less heat at low speeds, if it is PWM.
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If it's just a typical DC motor with two leads, apply 12V and it should run full speed. You could also measure how many amps it draws when running. That is, IF it's just an ordinary motor.
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On Fri, 22 Mar 2013 08:37:14 -0700, snipped-for-privacy@optonline.net wrote:

That makes a lot of sense!
Plus, it's easier to hook up leads to the harness connector than it is to get a DMM lead on the impossibly hard-to-get-to 40Amp Fuse F76 for the blower motor.
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Clive

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