Dead FET Power Transistors
 

I am trying to find a component part number or a schematic for a Blower
Control Board for a 1989 BMW with a 535i engine. The board has the number
275 526. L 06 stamped on it, and the Control Assembly has the name BEHR and
the numbers 90 . 947 . 00 . 842, E 3264/11 and 1 388 629 . 2 stamped on it.
There are four (4) blower motor settings on the control switch and only one
(1) works...High Speed! Anyone that can let me know where to find the
replacement FET transistors on the board would be of tremendous help. The
four (4) FET's are all the same. I have looked at the transistors under a
magnifying glass and can find no numbers stamped on them. I do not know if
they are made by an European Manufacturer or not. I also do not know whether
the FET's or N or P type or MOSFET's, etc. Any help as to the source of this
information would be very appreciated.
Thanks!

Dead FET Power Transistors
 

You would have to know the exact required specs, and patiently search
through data sheets to find the appropriate replacement. If these
transistors are blown, you must also find the cause, and fix that as well.
Maybe the device that is driving or loading them is also faulty, and this is
the reason for the failure.

As for automotive parts, the manufactures use their own house numbers on the
parts, and also have many of them custom made for their applications. The
dealers normally service at the modular level. They very rarely do anything
at the component level. This is why your dealer most likely will not be
able to supply these parts individually.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Robert L. Milton, Sr." wrote in message
om...
I am trying to find a component part number or a schematic for a Blower
Control Board for a 1989 BMW with a 535i engine. The board has the number
275 526. L 06 stamped on it, and the Control Assembly has the name BEHR and
the numbers 90 . 947 . 00 . 842, E 3264/11 and 1 388 629 . 2 stamped on it.
There are four (4) blower motor settings on the control switch and only one
(1) works...High Speed! Anyone that can let me know where to find the
replacement FET transistors on the board would be of tremendous help. The
four (4) FET's are all the same. I have looked at the transistors under a
magnifying glass and can find no numbers stamped on them. I do not know if
they are made by an European Manufacturer or not. I also do not know whether
the FET's or N or P type or MOSFET's, etc. Any help as to the source of this
information would be very appreciated.
Thanks!

Dead FET Power Transistors
 

Robert,

Unfortunately, I have to agree with Jerry, it is not likely that you'll
get a spec. Your best bet, besides paying BMW their price is to go to a
junk yard (aka Automotive Recyclers) and get another module. You can
find several that specialize in BMW's in the BMW car club of America's
(BMWCCA) magazine "Rondel".

Regards,
Tim Schwartz


"Robert L. Milton, Sr." wrote:

I am trying to find a component part number or a schematic for a Blower
Control Board for a 1989 BMW with a 535i engine. The board has the number
275 526. L 06 stamped on it, and the Control Assembly has the name BEHR and
the numbers 90 . 947 . 00 . 842, E 3264/11 and 1 388 629 . 2 stamped on it.
There are four (4) blower motor settings on the control switch and only one
(1) works...High Speed! Anyone that can let me know where to find the
replacement FET transistors on the board would be of tremendous help. The
four (4) FET's are all the same. I have looked at the transistors under a
magnifying glass and can find no numbers stamped on them. I do not know if
they are made by an European Manufacturer or not. I also do not know whether
the FET's or N or P type or MOSFET's, etc. Any help as to the source of this
information would be very appreciated.
Thanks!

Dead FET Power Transistors
 

"Robert L. Milton, Sr." wrote in message
om...
I am trying to find a component part number or a schematic for a Blower
Control Board for a 1989 BMW with a 535i engine. The board has the number
275 526. L 06 stamped on it, and the Control Assembly has the name BEHR
and
the numbers 90 . 947 . 00 . 842, E 3264/11 and 1 388 629 . 2 stamped on
it.
There are four (4) blower motor settings on the control switch and only
one
(1) works...High Speed! Anyone that can let me know where to find the
replacement FET transistors on the board would be of tremendous help. The
four (4) FET's are all the same. I have looked at the transistors under a
magnifying glass and can find no numbers stamped on them. I do not know if
they are made by an European Manufacturer or not. I also do not know
whether
the FET's or N or P type or MOSFET's, etc. Any help as to the source of
this
information would be very appreciated.
Thanks!

Maybe a moot point, given the other answers to your question, but if there
are no identifying markings, how do you know that they are FETs? I totally
agree with the others that piece parts such as those transistors, are
virtually unobtanium, especially from the manufacturer. If you're intent on
finding replacement transistors, perhaps your best bet would be to find a
copy of the shop service manual for your car. Be sure that you get one that
has the complete electrical schematics and parts lists. There may be a
partial schematic in there, but in all liklihood, there won't be enough
detail to give enough info to identify the components.
Go to a junkyard and find the complete module. That's probably your least
painful route.

--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!

Dead FET Power Transistors
 

First is the fan on or off all the time
Next is it a FET and is there flyback diode across it they can also short.
Does the voltage that controls the FET work properly (might not be the FET)
If it is the FET find out the starting current for the fan and check with
Digi-Key or other supplier and pick a power FET that will handle that
current, for a car the voltage is a lesser concern but pick at least a 100V
unit.
Remember to put a flyback diode across it if there isn't one and a transient
voltage suppressor as well 24V would be good.



"Robert L. Milton, Sr." wrote in message
om...
I am trying to find a component part number or a schematic for a Blower
Control Board for a 1989 BMW with a 535i engine. The board has the number
275 526. L 06 stamped on it, and the Control Assembly has the name BEHR
and
the numbers 90 . 947 . 00 . 842, E 3264/11 and 1 388 629 . 2 stamped on
it.
There are four (4) blower motor settings on the control switch and only
one
(1) works...High Speed! Anyone that can let me know where to find the
replacement FET transistors on the board would be of tremendous help. The
four (4) FET's are all the same. I have looked at the transistors under a
magnifying glass and can find no numbers stamped on them. I do not know if
they are made by an European Manufacturer or not. I also do not know
whether
the FET's or N or P type or MOSFET's, etc. Any help as to the source of
this
information would be very appreciated.
Thanks!

The FET is a type N 60V 14A - BUZ 71S3 but you can replace for the regular BUZ 71 (the diference is instead of 60V is 50V)

The IC is a LN2903 - Dual differential comparator - http://www.fairchildsemi.com/ds/LM%2FLM393.pdf

Dead FET Power Transistors
 

How do you know the FETs are bad? Did they explode?

FETs tend to fail shorted, so the more likely symptom of a bad FET
would be that the fan runs at nearly top speed on all settings.

I'd go check out the on-line junkyards if you can lower yourself to do
so.