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  #1  
Old 09-08-2010, 08:27 PM
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Join Date: May 2007
Location: Richardson, TX
Posts: 50
w124 Blower Motor, variable voltage on yellow of 3 pin connector

I have read through most of the blower motor threads but can't find the answer to my question... Any help is greatly appreciated.

My car is 87 W124 (300e) with the two speed blower. I've done most of the usual stuff:

strip fuse on strut tower is ok--good voltage on both sides
fuse 7 for climate control was replaced as well

I was not getting any air at all from the vents even though I could feel cold air from AC at high speeds. Nothing from defrost either.

My buddy had a spare blower motor so I decided to go ahead and replace mine since it was loud before it quit. So, that was done tonight.

My problem is this: I get low speed fan only now. Before I got nothing, now it's low speed only.

I checked the voltage at the three pin connector and get strong 13+ on the red pin.

My question is this: what should the voltage at the yellow pin be with the fan on high? what about on low? The voltage reading on high is 7.3V and on low is barely over 1V. I can't help but think it should be at least 12V on high in order to really crank that blower... Am I thinking right on this?

I've wondered if I have a bad voltage regulator but it seems like the voltage at the yellow pin should be a lot higher.

Thanks in advance!
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'87 300E 135K Miles
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  #2  
Old 09-08-2010, 09:30 PM
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Location: Richardson, TX
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blower voltage

So I've searched more and it seems as though 2-8V on the yellow pin is what it should be. Arthur Dalton's got several posts which indicate as much so I'll take that...

When I took my blower motor off, the cages did not spin freely. They were very hard to turn by hand. The new one spins freely... I'm thinking a bad blower motor burned out the regulator. It had been squeaking for 18+ months before it quit...

I didn't read Arthur's post until later (like a dummy I put it all back together...) but it seems as though I need to jump the blue wire on the blower to ground and if I get high blower speed, the regulator is bad. Since I've verified abt 2V and 8V at the yellow pin, the blue wire jumped to ground looks like the next thing...

Will get that done and post back.
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'87 300E 135K Miles

Last edited by TSH24; 09-09-2010 at 06:16 AM.
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  #3  
Old 09-09-2010, 01:04 AM
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Join Date: May 2009
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Id replace the strip fuse before i would trouble check anything. If you had a bad motor those fuses crack and slow pop so can be real intermittent. You replace that then test but if the motor doesnt turn after that correctly replace the regulator it is very common.
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  #4  
Old 09-09-2010, 09:35 AM
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Location: Northeast Indiana
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Where are you in Indiana? I likely have a spare that you can use for troubleshooting.
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  #5  
Old 09-09-2010, 10:57 AM
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I'm in Fort Wayne
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'87 300E 135K Miles
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  #6  
Old 09-09-2010, 11:17 AM
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I'm not that far away in Angola, I'll look to see if I have my spare here some time tonight.
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  #7  
Old 09-17-2010, 05:26 PM
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Finally tore the car apart again to jump the blue ground on blower--it blows full speed when grounded direct. Time for new regulator...
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