Fixed my 'Sword' fan speed controller

Well after several weeks of having nothing but maximum blower speed available I decided it was time to investigate one of the common quirks of the E34/E32 series... the 'Sword' module. As the fans variable speed control would work very occasionally (even if only for a few seconds) I realised that it wasn't a case of blown Mosfet transistors but most likely a suspect solder joint, probably where the connector socket joins the PCB. Well a crook joint it turned out to be, but not the connector. It was a capacitor as marked.

It took a while to trace. I removed the sword module from the climate control box, but left it plugged in. By setting the fan controller about midway and flexing the PCB I could cause the fan to cut in and out. After re-soldering the connector joints I retested it but no joy. Still the same. Finally I pushed a prodded each component on the PCB until I narrowed it down to the said capacitor. The slightest touch to this triggered the intermittant operation. I resoldered the capacitor and VOILA! Sword fixed!! :)

http://clients.net2000.com.au/~rowmat/BMW/sword_pcb.jpg

...I've never seen that fix before. Another one for the archives.

regards
Phil

Great sleuthing, thanks for posting it. I have a few more pic's on page 1 of the bimmer.info 7 forum. Similar re-flow-the-solder-fix solved my intermittent blower motor.

Anyone on this thread know what years the "sword" can be found on (as opposed to box-shaped resistor)? Thanks

'89-'90 certain. May have been phased to new style in '91.

Hi
My car is an E34 525i of year 1990 (july). I had "the" sword problem as a lot...
The old BUZ71 were out of order and I changed them with BUK9518 that are damn much better (Rdson only 0.018 ohm instead of 0.1 ohm). The result is perfect with
no longer overheating problem.
The sword was mounted at that time on cars with automatic A/C system.

Well Done!