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Scott Dorsey Scott Dorsey is offline
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Default Root cause insight into the common BMW blower motor resistorfailures

Bimmer Owner wrote:
On Thu, 21 Mar 2013 11:45:54 -0400, Scott Dorsey wrote:

Static resistance doesn't tell you anything, but operating current
measured with a DMM would tell you a lot.


It 'can' be done, but would require a test jig inserted inline
as the FSU is deeply ensconced under the dash while the blower motor
is even more deeply so.


I don't know the wiring diagram on that particular model, so I don't know
where you would need to break in to measure just the current of the blower
without anything else. But it does not seem terribly insurmountable,
especially seeing that BMW is very good about breaking everything out into
connectors all over.

I've never tested one, but I put a drop of turbine oil on the
motor bearings every five years or so.


While that preventive work might be prudent, the sheer effort
to remove the entire dash simply to access the blower motor
would be problematic.


Well, that's partly why I drive a 2002 and an E28, everything is much
easier to get to.

Still, if the problem is that the blower motor is merely using more
current as it gets older, why wouldn't a NEW FSU burn up within a
few weeks of insertion?


You would expect that, indeed.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."