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A/C e24 - six



From: Norman Hom {hom_lanihau@juno.com}
Date:  Sept. 13 96
Subject:  A/C on a E24 - 633

Would any body have access or know anyone parting out a '83 to '88 six. 
I need an A/C blower fan switch for my '84 633.  I do not think the
5-series used the same switch.  My parts price lists does not list any 5s that use the same part.

My  fan only blows on high.  The blower switch has an internal  switch which cuts full power to the blower motors (either air or heater fan).  The
back portion of the blower fan switch has the electronic portion for the resistors, transistor and potentiometer switch which regulates the fan
speed from low to high.  I tried replacing the transistor but no help. 
I have a replacement potentiometer switch, but I have not tried it yet. 
The potentiometer is not an exact fit as it is not constructed like the old one and will not allow me to hook it up to the switch nob to tune the voltage.  So far the two replacement componets have only cost $2.95 and $.75.  Cheap but not factoring in my time.  A new switch lists for $101. 
I would like to try fixing the old one or find a used one before going
to the BMW dealer.

My other alternative is to run one or more resistors to the full power switch wire that runs to the blower motor and add a switch to cut the
resistor(s) in or out to slow down the fan.  If I went this route, what
can kind of component be used like a fuse as a safety switch in the
event of an overload on the resistors?  Reviewing the wiring diagrams
for my '85 318i, there is a safety switch on the resistor board if the
resistors overload.  

Any electrical engineers or the like out there that can give me some help
on the technical aspects of how resistors work to slow down the blower
motor and  or how to test the original electronics in the old switch.  I
understand that you can not test the resistors without pulling one side
out from the circuit board.  I tested each resistor with an ohm meter on
the board and each showed ohms.  I must have an open circuit on the old
board, but how can I tell which component?  The alternative is to
replace all 8 resistors,  but that seems to be a bit much.  Any advise
would be appreciated.

aloha - TIA (thanks in advance) 
I am new on the list but have figured out a few of the acronyms.  By the way, what does BTW stand for?

Great BMW info on the list.


Norman
Honolulu, Hi
'84 633csi
'85 318i
hope to someday afford an '89 635

please respond directly to 
hom_lanihau@juno.com