Hi folks I have gone threw posts on fan motors and have a couple of questions, first dose the 90 model have the resister to control the fan speed? My wife came in today and informed me that the blower only runs at the low speed,she said that it happened to her some time last week too, but that when she arrived at home it suddenly jump up in speed and had no more trouble till today, Can any one give me a direction to look in? maybe the temp wheel, or motor itself, Thanks JNT



UMM,UMM, GOOD

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According to the parts catalog above, yours has a blower regulator http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2DM1BXZHD2DM1BY3X2&year=1990&make=MB&model=420-SEL-001&category=R&part=Blower+Regulator

Not cheap. Since it returned to normal speed, it might not be the regulator - thing is, I honestly don't know what direction to point you in (sorry).

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

The blower regulator is an electronic (transistor) control of the negative side of the circuit. From the blower's standpoint it looks like an infinitely variable resistor. The degree of resistance is directly related to the voltage control signal from the push button controller. A one to six volt control voltage is measured as the control is moved from low to high position. If the control voltage is appropriate and the speed is not the circuit can be bypassed to prove the blower is capable. If control exists and the blower can run full speed then the regulator is the problem. Electrically the the regulator can be monitored by watching the voltage drop across it.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

OK I get the point, I was thinking of the temp wheel not functioning, telling the system that it has found the correct temp. and slows the motor, maybe I am wrong!