On Tuesday, February 4, 2014 11:11:36 AM UTC-5, wrote:
Hi i just bought an fsu from behr for my 2002 e46 and i opened it . Inside was only one transistor 2n0605 from infineon and an elmos 10901d.The 2n0605 is 80 amps 55v mos.I am now working to figure out the exact schematics

Out of curiousity, how did you open it up? The ones I've seen
are potted in 1/2" deep epoxy, with no obvious way to get that out
without destroying what's inside....

Also, Ive been helping a friend with the FSU problem. His blower
went from working fine to not working at all. Being concerned about
all the apparently crap ones out there, bought one from a BMW dealer
that is marked Sitronic. It appeared to work, but..... With the
blower on high it will run all day, no problem. You can back the blower
off to about 80% and as you do so, the heat sink starts to get very
hot, but the blower still runs at 80%. If you back the speed down
anymore, it gets even hotter and then starts pulsating the blower,
finally stops all together. I tried dipping the end of the heatsink
rods into a container of water when it does that and within a couple
seconds the blower starts working again fine. So, it's definitely
heat related.

Any ideas on what's wrong? First impression would be that it's the new
FSU because the blower works on full or near full speed. But I guess
the other possibility is that the motor has a problem? Seems odd
though that a single winding type DC motor could run fine at full
speed, but then cause the FSU to overheat at lower speeds.