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Thread: Question about the sword MOSFETS

  1. #1
    Join Date
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    Question about the sword MOSFETS

    I've been troubleshooting intermittent heater blower operation on my 1989 525i. So far I (think) I have this:

    Blower brushes: worn, but still working
    Blower bearings: OK
    Wiring: intact, no breaks
    Heater controls (dial type): working
    All contact services: clean
    Fuse: Good
    Sword: looks like a sword

    The blower has always worked on 4 and been intermittent on the other speeds. Recently, even on 4, the blower will work intermittently, randomly turning on and off.

    I looked at the information Shogun and others have collected, but cannot find a fix for intermittent operation on 4. Would this indeed be a sword issue that requires new MOSFETS, respray etc./ a new sword, or am I overlooking something? Are there resistors on the '89 that I don't know about?


    King of the low budget sig

  2. #2
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    good question, sounds like sword problems. If you can find a know good spare I would substitute that first. Other than that...dunno

  3. #3
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    Yeah, there's a sword repair somewhere online with part numbers. Sounds like what you need.

    Go ahead and bite. Plenty for everyone.

  4. #4
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    SWORD
    My friend Wolfgang in Germany has an excellent site for that,
    http://www.e32-schrauber.de/bmw/s-heizschwert.htm
    even how to test the sword, and also including sword repair links to our japanese repair sites.
    SHOGUN'S TRICKS AND TIPS FOR THE SEVEN SERIES
    http://twrite.org/shogunnew/topmenu.html

  5. #5
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    Quote Originally Posted by shogun View Post
    SWORD
    My friend Wolfgang in Germany has an excellent site for that,
    http://www.e32-schrauber.de/bmw/s-heizschwert.htm
    even how to test the sword, and also including sword repair links to our japanese repair sites.

    Thank you, that's not the one I was thinking of, but it will certainly help. It should be in the DIY sub.

    Go ahead and bite. Plenty for everyone.

  6. #6
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    next try ;-)

    3 symptoms I know of and there may be more:
    1. Fan runs on high no matter what position including off: One or more MOSFETS have shorted.
    2. Fan only works on high: one or more MOSFETS have failed.
    3. Fan works okay but only if you place it in the high position then roll it back into the desired position every time you start the car. One MOSFET tests open.

    Here is the Final stage unit before getting serious.
    http://www.bimmerboard.com/members/s...word%20024.jpg
    If you have the creamy epoxy shown in the first picture simply use a pair of side cutters and get under it and 'snip' it off. It comes off quite nice in one chunk. If you have the 'clear' epoxy you can snip it off (it isn't as brittle and needs a little more work) or use some heat to soften it and easily pop it all off with a screwdriver.
    http://www.bimmerboard.com/members/s...word%20033.jpg
    Back of the PC board with epoxy removed.
    http://www.bimmerboard.com/members/s...word%20025.jpg
    simple solution to purchasing standoffs and other items. Drill out each rivet with a 5/64 bit. Then 'countersink' each rivet on both sides with a 3/16. This allows you to use a 2mm x 18 mm screw and the existing standoffs.
    http://www.bimmerboard.com/members/s...word%20027.jpg
    I drilled a hole in the wood to accept the temp sensor nut so the 'sword' would sit level.
    http://www.bimmerboard.com/members/s...word%20028.jpg
    then drilled each rivet out with the 5/64 bit.
    http://www.bimmerboard.com/members/s...word%20029.jpg
    Then I used the 3/16 to remove enough rivet on each side so the PC board could be separated from the heat sink.
    Desolder the 3 pins on each MOSFET.
    http://www.bimmerboard.com/members/s...word%20026.jpg
    Remove the nut on the temp sensor. Be certain to hold the inner side so you don't twist it. Now gently pry it apart.
    http://www.bimmerboard.com/members/s...word%20032.jpg
    http://www.bimmerboard.com/members/s...tage%20001.jpg
    MOSFETs
    http://www.bimmerboard.com/members/s...tage%20002.jpg
    I have a tool to bent the leads but any straight edge will do the trick
    http://www.bimmerboard.com/members/s...tage%20003.jpg
    Bent to the proper shape
    http://www.bimmerboard.com/members/s...tage%20004.jpg
    Install the ready to go standoff
    http://www.bimmerboard.com/members/s...tage%20005.jpg
    And insert into the PC board
    http://www.bimmerboard.com/members/s...tage%20006.jpg
    Solder them in place then use the 2mm x 18mm screws, washers, and nuts in place of rivets to assemble.
    http://www.bimmerboard.com/members/s...word%20034.jpg
    Install the temp sensor nut and the circuitboard cover and it's good as new!


    You do not need to reaply the epoxy covering. it is used specifically for tamper control as the entire assembly is coated. You do need to reapply the Conformal Coating.
    http://www.bimmerboard.com/members/s...tage%20009.jpg
    This can be purchased as a spray or brush on application.
    When testing the final stage unit I noticed a poor ('scratchy')signal from the control. This can possibly affect the final stage unit so I removed it and cleaned the speed control internals with Control Cleaner also pictured.
    SHOGUN'S TRICKS AND TIPS FOR THE SEVEN SERIES
    http://twrite.org/shogunnew/topmenu.html

  7. #7
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    Quote Originally Posted by shogun View Post
    next try ;-)

    3 symptoms I know of and there may be more:
    1. Fan runs on high no matter what position including off: One or more MOSFETS have shorted.
    2. Fan only works on high: one or more MOSFETS have failed.
    3. Fan works okay but only if you place it in the high position then roll it back into the desired position every time you start the car. One MOSFET tests open.

    Here is the Final stage unit before getting serious.
    http://www.bimmerboard.com/members/s...word%20024.jpg
    If you have the creamy epoxy shown in the first picture simply use a pair of side cutters and get under it and 'snip' it off. It comes off quite nice in one chunk. If you have the 'clear' epoxy you can snip it off (it isn't as brittle and needs a little more work) or use some heat to soften it and easily pop it all off with a screwdriver.
    http://www.bimmerboard.com/members/s...word%20033.jpg
    Back of the PC board with epoxy removed.
    http://www.bimmerboard.com/members/s...word%20025.jpg
    simple solution to purchasing standoffs and other items. Drill out each rivet with a 5/64 bit. Then 'countersink' each rivet on both sides with a 3/16. This allows you to use a 2mm x 18 mm screw and the existing standoffs.
    http://www.bimmerboard.com/members/s...word%20027.jpg
    I drilled a hole in the wood to accept the temp sensor nut so the 'sword' would sit level.
    http://www.bimmerboard.com/members/s...word%20028.jpg
    then drilled each rivet out with the 5/64 bit.
    http://www.bimmerboard.com/members/s...word%20029.jpg
    Then I used the 3/16 to remove enough rivet on each side so the PC board could be separated from the heat sink.
    Desolder the 3 pins on each MOSFET.
    http://www.bimmerboard.com/members/s...word%20026.jpg
    Remove the nut on the temp sensor. Be certain to hold the inner side so you don't twist it. Now gently pry it apart.
    http://www.bimmerboard.com/members/s...word%20032.jpg
    http://www.bimmerboard.com/members/s...tage%20001.jpg
    MOSFETs
    http://www.bimmerboard.com/members/s...tage%20002.jpg
    I have a tool to bent the leads but any straight edge will do the trick
    http://www.bimmerboard.com/members/s...tage%20003.jpg
    Bent to the proper shape
    http://www.bimmerboard.com/members/s...tage%20004.jpg
    Install the ready to go standoff
    http://www.bimmerboard.com/members/s...tage%20005.jpg
    And insert into the PC board
    http://www.bimmerboard.com/members/s...tage%20006.jpg
    Solder them in place then use the 2mm x 18mm screws, washers, and nuts in place of rivets to assemble.
    http://www.bimmerboard.com/members/s...word%20034.jpg
    Install the temp sensor nut and the circuitboard cover and it's good as new!


    You do not need to reaply the epoxy covering. it is used specifically for tamper control as the entire assembly is coated. You do need to reapply the Conformal Coating.
    http://www.bimmerboard.com/members/s...tage%20009.jpg
    This can be purchased as a spray or brush on application.
    When testing the final stage unit I noticed a poor ('scratchy')signal from the control. This can possibly affect the final stage unit so I removed it and cleaned the speed control internals with Control Cleaner also pictured.
    again you make us all feel mortal....

    P.S. Received my reset tool yesterday. many thanks

    Byron

  8. #8
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    Who the hell is Byron?

    Go ahead and bite. Plenty for everyone.

  9. #9
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    Quote Originally Posted by Binjammin View Post
    Who the hell is Byron?
    Oops, my secret identity is loose.....

  10. #10
    Join Date
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    1989 525i, Delphin/Black
    WOW, thanks shogun, I have my work set out . Your write ups should stickied if they have not been already.


    King of the low budget sig

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