Author Topic: blower speed control (Read 3791 times)

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?

inarticulate is · « **Reply #1 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.

dvmotorsports · « **Reply #2 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.

DesktopDave · « **Reply #3 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.

dvmotorsports · « **Reply #4 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.

DesktopDave · « **Reply #5 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?

dvmotorsports · « **Reply #6 on:** January 29, 2010, 02:44:01 PM »

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