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Old 04-24-2008, 02:32 PM
riro424 riro424 is offline
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Location: Chicagoland
Join Date: Oct 2007
Posts: 187
Mein Auto: 2003 525i
Originally Posted by bluebee View Post
The question becomes what to test once the FSU is in our hands. Do we have a WIRING DIAGRAM?
Oh well ... If I end up getting a new FSU (I'll wait to see if it goes out AGAIN), you can rest assured I'll ohmmeter it while both are in my hands!

If the FSU is merely a bank of resistors, we'll see a short or open; if it's a bunch of power transistors, I'm not sure what we'll see ... as we might have to bias the transistors to get it to show it's mettle ... either way ... let's begin to gather the data starting with the very next person who has a bad and good BMW FSU and/or blower motor in their hands!!!!!

Here's the FSU wiring diagram from Bentley:

Unfortunately, it is full of transistors, and these intermittent problems are tough to troubleshoot.

F76 - Fuse 76
15 - Ignition power (RUN & START)
30 - Batt positive (+)
31 - Batt negative/gnd (-)
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Last edited by riro424; 04-24-2008 at 02:35 PM.
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