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  #1  
Old 08-12-2002, 05:00 PM
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Location: Florida
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Burning smell inside cabin-blower motor related??

My ac clutch/blower motor/acc unit fuse blows at least once a day. I now get a burning smell inside the cabin, and i'm not sure if it's due to the fuse melting and blowing or wiring. On the fuse box cover there is always black and white residue from the fuse, and the fuse is always melted, not just blown. I did a few tests to see if i could isolate the problem and here is the tests i ran and their conclusions
1. Without the car on i turned on the a/c, blower to high, the fuse got extremely hot extremely fast
2. With car on, blower motor on low, fuse did not get hot at all, and the a/c compressor was on
3. With the blower motor on "auto" the fuse gets mildly hot, but not so hot as to burn you.

Based on those tests, i took out the blower motor and had a look see at the bearings, armature, and brushes. The brushes looked fine, the armature looked fine, and the bearings were fine as there was NO PLAY whatsoever between the fan blades and the motor. The motor doesn't sound bad, or overly loud, and puts out the "normal" air for a W126 car. Whats going on here???? i'd really like to smell nice clean air and not burning stuff through my a/c vents! thanks
RYan

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  #2  
Old 08-12-2002, 05:26 PM
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Location: Houston, Texas
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You might have a short in the windings. Shorted windings will cause the motor to draw excessive current, get hot, give off a bad odor and not run properly. The only way to test a motor is to measure the current for a given mechanical load condition and compare those values to a known good motor.

The fact that it is blowing fuses and making a smell tells me that it is probably a bad motor.
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  #3  
Old 08-12-2002, 08:35 PM
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Ryan,
Belive it or not your fuse box is connected to the cabin air! Climate controled fuses. When the fan runs on high for extended periods of time the fuse will get very hot, this combined with a little corrosion on the fuse holder tabs can cause enough heat to melt the plastic. In my wifes car (she insists that she will suffocate if the fan isn't blowing on high) I've installed an after market fuse holder for the blower motor in an open spot in the back of the fuse box. My 300SD blower fuse looks like new and the third car shows some small deformation.

Bob DuPuy
3 300SDs
3 Unimogs (arriving USA 8/15 !!)
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  #4  
Old 08-13-2002, 01:43 AM
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hmm, that is a very, VERY good idea H2odiesel(how ya been anyway?). It is kind of deformed and messed up looking. Could i rig the same thing for my aux fan? (it got deformed when the bearings were going). And also, do you mean to tell me that the cabin air actually FLOWS through the fuse box? is that in an effort to keep things cool?? IF so, thats definately the smell! wow this night is getting better and better.... what kind of fuse holder do you recomend, just one from radio-shack?? thanks again!!
Ryan
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2002 330i.........current.
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  #5  
Old 08-13-2002, 05:58 AM
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No reason you couldn't use one for the fan too. I used a sealed holder for a glass tube type fuse, made by Little Fuse. With the lid to the fuse box open you'll see a couple screws inside the front edge, remove these and the upper section of the box lifts up. Identify the correct wires from underneath and cut them loose. I used a heat shrink type crimp connector to splce them on to the new holder. There is plenty of room in the back of the fuse box for the new holder in spots were gas models have additional relays. NOTE- you should disconnect the battery before you start poking around in the fuse box.

Bob DuPuy
Parrish, Fl
3 300SDS
3 Mogs

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