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Thread: E31 M70 motronic 1.7 MOSFET reference needed

  1. #1
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    E31 M70 motronic 1.7 MOSFET reference needed

    Hi

    I got an issue on one of the DME motronic 1.7 of my 1991 E31 M70.
    Smoke was going out from one of the DME and also the corresponding coil was smoking.....

    I have open the DME, found a burned MOSFET, but i was not able to find the reference of this components on the web.
    I suppose it was a internal BOSCH reference. Does someone know a compatible MOSFET reference i can use ?

    IMG_4292.jpgIMG_4295.jpgIMG_4296.jpg

    Thanks

  2. #2
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    Had a 1991 BMW 850

  3. #3
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    Bad coils will do that.
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
    ALPINA B7 -Alpinweiß III


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  4. #4
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    @rjjablo Thanks for the link, but i am looking for the MOSFET reference only

    - - - Updated - - -

    Quote Originally Posted by TxGR8White View Post
    Bad coils will do that.
    Yes i confirm,, the coil is dead.

  5. #5
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  6. #6
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    There's oodles of equivalents - but TIP 162 worked for me:

    https://uk.farnell.com/multicomp/tip...295?ost=tip162

    ...or on Amazon:

    https://amzn.to/3f3FGtM

    Same as used on the V8's: https://www.meeknet.co.uk/E32/ECU/Index.htm
    Last edited by Timm; 11-15-2020 at 03:26 PM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  7. #7
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    Ok thanks for the MOSFET reference Timm.

  8. #8
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    Hi

    I received the new MOSFET, but its form factor need to be "tuned" to put it back in place inside the DME.

    IMG_4326.jpgIMG_4327.jpg

    The M70 is now running on 12 cylinders !
    Thanks

  9. #9
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    Well done! Yes, I had to do the same on my M60 - nothing a file won't sort out!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  10. #10
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    Not that it matters much for you as you have resolved the problem.

    But for those that are electronics professionals.
    The correct device type is everything in identifying the appropriate substitute device.
    See attached document.
    The device is not a MOSFET it is a NPN Darlington Power Transistor - SOT-93 package with the heatsink tab removed.

    My only suggestion in selecting a substitute is to make sure the back of the device looks the same as many devices have changed the package configuration over the years and the power dissipation ratings can be lower.
    I anticipate the original DME device has bare metal exposed on the back side for best heat dissipation to the heat sink.
    Some of the newer devices will be completely enclosed in plastic and hence the power rating is compromised.
    Also, make sure a heatsink compound is applied to the back of the device in contact with the heatsink.
    The heatsink compound substantially increases the heat transfer and thermal dissipation keeping the transistor cooler.
    Attached Files Attached Files
    Last edited by m6bigdog; 11-29-2020 at 12:52 PM.

  11. #11
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    E31 850iA 1992
    hese are special BOSCH transistors.
    ...buy a cheap DME (E30, E36...) and put that transistor to your DME.

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