On Mar 20, 11:08*pm, Bimmer Owner wrote:
Does anyone have insight into what is the root cause (and repair) of the
FSU failure that plagues almost every 1997 to 2003 BMW?
*http://www.bimmerfest.com/forums/att...entid=126060&d...

Also, does anyone have an idea HOW TO TEST a "repaired" FSU?

The "blower motor resistor", which also goes by FSR (Final Stage Resistor)
or by FSU (Final Stage Unit), is known to fry itself in almost every single
E46 (3-series), E39 (5-series), and E38 (7-series) BMW.
*http://www.bimmerfest.com/forums/sho...d.php?t=143393

The problem with replacing this ~$100 part is that the new replacement FSU
fries itself just as often as the old one did, so you end up repeatedly
replacing your fried FSU every few years or so.
*http://www.bimmerfest.com/forums/sho...d.php?t=528566

That's fine for most people (although the DIY is a PITA) - but I ask
this newsgroup whether anyone has any insight into WHAT is actually
breaking - and - why?
*http://www.bimmerfest.com/forums/sho...d.php?t=309399

Here is the best (admittedly sketchy) wiring diagram we have so far:
*http://www1.picturepush.com/photo/a/...g/12467819.png

I had a dodge caravan that fried its heater AC motor speed control
resistor repeatedly....

the connector to the wiring harness detoriates from the high current
and the voltage drop causes the connector to heat up and the entire
assembly fails.

Oddly enough I repair roll laminators that apply plastic film to paper
think menus

laminators experience similiar failures so I did the following.

Purchased a new resistor block, soldered wires on all the connectors
putting a heavy wire on each one.... Put a pigtail on each one.
Installed resistor block. Its screwerd to the fire wall.

Cut the plug assembly off the harness, stripped all wires, twisted
them together and installed wire nuts on each one.

had the van for years with zero problems for this part