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DISCUSSION => Electrical => Topic started by: 4banger on January 28, 2010, 09:44:36 PM

Title: blower speed control
Post by: 4banger on January 28, 2010, 09:44:36 PM

today my blower speed control went apeshit. it only works on high. anyone have any ideas what is the cause and solution?

Title: blower speed control
Post by: inarticulate is on January 28, 2010, 10:55:48 PM

Mine did the same thing a few months ago, but it recovered on its own and the symptoms haven't reappeared.

Title: blower speed control
Post by: dvmotorsports on January 29, 2010, 11:05:41 AM

The speed control switch has a resistor in it IIRC. The voltage variance controls fan speed. Probably just a bad switch. Check your junk yard. And I have one if need be.

Title: blower speed control
Post by: DesktopDave on January 29, 2010, 11:29:05 AM

There's a series resistor on the blower unit.  Any time you have the fan only working on full it's the series resistor (also called a blower resistor, final stage unit, or resistor pack).

Electric motors can't run at variable speeds unless they have a controller or resistor to cut the power input.  Different models of BMWs have both types.  You should see the final stage on the 7-series...quite the intricate circuit board there.

On e30's it's under a cover on the firewall. On the e36 it's in the passenger footwell.  Here's a writeup for the e36. (http://www.bimmerfest.com/forums/showthread.php?t=143393)

Title: blower speed control
Post by: dvmotorsports on January 29, 2010, 02:11:42 PM

Quote from: DesktopDave;86072

You should see the final stage on the 7-series...quite the intricate circuit board there.
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I had to rewire an entire E66 because of rodent damage. Took a week and a half.

Title: blower speed control
Post by: DesktopDave on January 29, 2010, 02:34:15 PM

Quote from: dvmotorsports;86083

I had to rewire an entire E66 because of rodent damage. Took a week and a half.

Sounds like a nightmare!  Could have been worse...at least you didn't have to see the outside of it for a week, eh?

Title: blower speed control
Post by: dvmotorsports on January 29, 2010, 02:44:01 PM

Yeah. Not very aesthetically pleasing. For 7's, I'm an E38 man.