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Old 04-09-2009, 02:55 PM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
Let's ask everyone to post resistance numbers & do an autopsy on the old BMW FSU

Doru pointed me to this thread from here and it's very intersting!

When I find what I did with my old FSU, I'm gonna see if I can take it apart to see what I can find out myself. I hope others do the same.

One recommendation for others (which I already made in the canonical E39 thread from Elvis) is for all of us to post the resistance measurements from the old and new FSUs. That way, we might find a pattern of interest.

Here is what I think each pin does:
#1 = ground
#2 = 12V power, 40 amp fused
#3 = input to fsu from heat/ac module
#4 = output power to the blower motor? (speed 1?)
#5 = output power to the blower motor (speed 2?)

And, here is what I measured between each pin and ground (the FSU body):
#1: Old FSU = 600Kohms, new FSU = 11.2 ohms
#2: Old FSU = 3.02Mohms, new FSU = 1.22Mohms
#3: Old FSU = 2.22Mohms, new FSU = 608Kohms
#4: Old FSU = 2.14Mohms, new FSU = 602Kohms
#5: Old FSU = 3.05Mohms, new FSU = 1.28Mohms

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