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  #1  
Old 05-15-2007, 07:30 PM
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W140 A/C Blower Motor

92 300SE

I think my A/C blower motor is headed for the great beyond.

On high fan setting, it draws about 35A. Is that too high, or OK? Can't find anywhere on AllData, or in my other documentation that gives me a clue.

I replaced the speed control with one of those advertised here on the site. However, when the fan runs for a long time on high, I smell a "cooking resin" odor in the air.

The smell is not of burning wire, its coming from the resin used to pot all of the electronics in on the control. I've pulled the filter cover off and sniffed to compare.

The wires all look OK - none shows signs of being hot, nor do they get excessively hot to the touch when the fan is on max.

So - what's the story - what should max amp draw be??

Thanks
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  #2  
Old 05-16-2007, 03:48 AM
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Quote:
Originally Posted by wbrian63 View Post
92 300SE
So - what's the story - what should max amp draw be??
Hello,

While not directly answering you question, at least supplied
voltage is listed here;
http://www.peachparts.com/Wikka/W140BlowerMotor

...and the comment from Dalton in this thread;
1994 S500V W140 HVAC BLOWER & BLOWER REGULATOR

br,
syljua
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1984 230E W123

Last edited by syljua; 05-16-2007 at 04:00 AM.
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  #3  
Old 05-16-2007, 09:53 AM
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Thanks for those links. I tried searching but didn't find either of those articles.

Dalton's response had the info I needed - 25A is the max draw for the blower, I'm pulling 35A at full speed - so a new motor is on order from FastLane. (MB wants $700+ wholesale for a new blower unit - but that comes with a controller included.)

Regards
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  #4  
Old 05-16-2007, 10:51 AM
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Quote:
Originally Posted by wbrian63 View Post
92 300SE
I think my A/C blower motor is headed for the great beyond.

On high fan setting, it draws about 35A. Is that too high, or OK? Can't find anywhere on AllData, or in my other documentation that gives me a clue.

I replaced the speed control with one of those advertised here on the site. However, when the fan runs for a long time on high, I smell a "cooking resin" odor in the air.

The smell is not of burning wire, its coming from the resin used to pot all of the electronics in on the control. I've pulled the filter cover off and sniffed to compare.

The wires all look OK - none shows signs of being hot, nor do they get excessively hot to the touch when the fan is on max.

So - what's the story - what should max amp draw be??

Thanks
If you run the blower on 'high', there's very little power dissipation in the regulator. . it's very low. The MAX power dissipation point is when the blower is a little below half speed. This is the point of the greatest heat generated in the regulator.

So if you smell something at high speed it shouldn't be the regulator.

Your car should have a 30amp fuse for the blower and, it draws about 25amps max, typically. If you measured "35amps", something is amiss?? You should have blown the fuse??? Did you actually measure that current (35amps)??
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  #5  
Old 05-17-2007, 09:30 AM
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I used an "amp clamp" around the positive wire to the blower when on high.

The fan is "stiff" - when you manually spin the squirrel cage, it stops abruptly. The bearing used to squeak on low, but a few drops of tranny fluid on the upper bearing got rid of the squeak.

According to the MB manual I read at the dealer the other day the (and I'm working from memory here) "blower is internally protected from short circuits - no external fusing is provided or required" I'm guessing that the regulator provides the protection in case of a short circuit in the motor.

To confirm this, I cracked open AllDataDiy, and navigated the rats-nest of wiring diagrams for the A/C system. Finding the blower motor, the red wire is 12v+ back to terminal block X/10, which is part of circuit 30. This circuit is unfused directly back to the battery. On a 140 sedan, it's on the floorboard, passenger side, beneath the protection plate.

So, in short (no pun intended), there is no fuse for the blower motor.

As for what load is on what item and when, I believe that both the wires for the blower (positive & negative) come from the regulator. If the blower is drawing too many amps (and from the other article linked to in this thread, it definitely is), something's gonna get hot. The odor I'm smelling is definitely the resin used to seal the electronics (I used to work in an industry that used just this type of stuff - I know the smell very well).

Having said that, Tuesday the car set out in the sun for quite a while at the mechanic's shop, so the A/C ran at full-tilt for at least 20 minutes cooling the car down (inside temp at asipirator was 118 when I started the car). I didn't notice the smell this time. It may be that the resin is "gassing off" a bit, and assuming I don't ruin the regulator before the new motor comes in from FastLane, I'm just going to keep using it.
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  #6  
Old 05-17-2007, 10:56 AM
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Draw of 35A isn't that high.

Look at chart
Attached Files
File Type: pdf BLOWER.pdf (38.5 KB, 208 views)
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  #7  
Old 05-17-2007, 02:11 PM
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That's the exact type of information I was trying to find at my local MB dealer the other day.

Where did you come across that tidbit of data??

I'll see how the values differ when I replace the motor I've already got on order.
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  #8  
Old 05-17-2007, 04:07 PM
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TDM=technical data manual
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  #9  
Old 05-17-2007, 06:42 PM
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Quote:
Originally Posted by wbrian63 View Post
I used an "amp clamp" around the positive wire to the blower when on high.

If the blower is drawing too many amps (and from the other article linked to in this thread, it definitely is), something's gonna get hot. The odor I'm smelling is definitely the resin used to seal the electronics (I used to work in an industry that used just this type of stuff - I know the smell very well).

Having said that, Tuesday the car set out in the sun for quite a while at the mechanic's shop, so the A/C ran at full-tilt for at least 20 minutes cooling the car down (inside temp at asipirator was 118 when I started the car). I didn't notice the smell this time. It may be that the resin is "gassing off" a bit, and assuming I don't ruin the regulator before the new motor comes in from FastLane, I'm just going to keep using it.
That's the best way to measure the current . . I have a Fluke and it works well but the accuracy of it (and yours) I suspect is +/- 5% or worse. When I measured my it was more like 26 amps or so.

If the blower was on HIGH, there's very little power dissipation in the regulator. So maybe that's why you didn't smell anything.
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  #10  
Old 05-27-2009, 11:06 AM
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Could be worse. Dusted my 140 off for a nice drive only to discover that the blower was not working at all.
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  #11  
Old 05-27-2009, 02:49 PM
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If it squeeked, and now does not spin freely it is an indication of the bearings being bad /cororroded. Maybe you are smelling the armature of the motor overheating.
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  #12  
Old 05-27-2009, 02:55 PM
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Check the fuse link..common on a car that has sat...
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  #13  
Old 05-27-2009, 07:29 PM
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Quote:
Originally Posted by Arthur Dalton View Post
Check the fuse link..common on a car that has sat...
Arthur,

Thanks for the suggestion. I was planning a service visit soon anyway and was just going to have my mechanic look at it but a quick peek might save everyone a bit of hassle.
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  #14  
Old 05-27-2009, 07:31 PM
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Should be over by the drivers side strut tower..little back box with a fuse link inside..they get a hairline crack you can't see, but if you jumper it and the blower comes ON , that is the problem
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  #15  
Old 05-27-2009, 08:39 PM
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I would just replace the blower motor (Behr) and be done with it...the fuse is an 80 amp...by far the largest I've ever seen on a car. I just went through this with a 1990 300TE and actually pulled a used blower from a 1993 300E that cost me $15...problem solved...good luck
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