Question about the sword MOSFETS

[DIL]

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?

[zubbie]

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

[Binjammin]

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

[shogun]

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.

[Binjammin]

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.

[shogun]

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.

[zubbie]

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

[Binjammin]

Who the hell is Byron?

[zubbie]

Who the hell is Byron?

Oops, my secret identity is loose.....

[DIL]

WOW, thanks shogun, I have my work set out . Your write ups should stickied if they have not been already.