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Old 02-26-2008, 04:36 PM
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Join Date: Mar 2004
Location: ILLINOIS
Posts: 348
w140 heater/ac blower

I just got a w140,early model,1992,with a dead blower motor.I grounded the blower directly and it works,full speed,so,I assume regulator is faulty.The one on the car is a Behr,I dont know if that was the factory model,before I spend 100$+ for another one,is there anything else worth checking?ACC seems working,I can hear switching vents when I push the buttons also it will turn the AC compressor on if set on defrost...

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Old 02-27-2008, 10:05 AM
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Join Date: Aug 2006
Location: Houston, TX
Posts: 450
I'd stick with the behr. Use the Buy Parts link here on the forum - they've got a good price and it helps support this wonderful site.

I have a '92 300SE as well - and I've been "through" that car from nose to tail (bonnet to boot?). Don't hesitate to PM me with questions when they come up.

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Old 02-27-2008, 11:19 AM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,804
Grounding the motors neg. side simply means you have taken the switched ground control circuit out of the system. [ by-passed]
So , you MAY have a bad regulator, but you could also have no variable trigger voltage to the regulator. The regulator has to have a trigger signal in order to complete the blower ground circuit. No trigger sig =no blower.
You want to check the 3 wire connector at the firewall , behind the brake booster. You need var/voltage at yellow wire for the reg to work.
The wires there are rd/blk/yl.
r to blk-12v
y to blk- var 2-8 volts , depending on speed selection.
If no var voltage at yellow, then the problem is upstream from that connector, not downstream/regulator...

A Dalton

Last edited by Arthur Dalton; 02-27-2008 at 11:37 AM.
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