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Default Root cause insight into the common BMW blower motor resistor failures


"Bimmer Owner" wrote in message
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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.