1991 400 SE blower fan not working- please help!

[iwona]

Hi, can anyone please help with this one, please
Mercedes '91 400SE, fan stopped working- checked fuses, all ok, purchased fan blower resistor regulator- when replaced fan works at full speed constantly even when ignition is off, and the only way to turn it off is to disconnect the battery. I'm totally confused now, I was hoping that replacing regulator will solve the problem, I've read that thermal paste should be used? is that true? What else should I try? any advice would be much appreciated.
Iwona

 

[television]

If the motor runs flat out all the time then the regulator has a short if it is the sealed solid state type, the regulator can be tested on an ohmmeter where a diode effect should be present on any pin,, a short circuit reading is a fail

 

[iwona]

Thank you for your reply, just checked it today and readings are 12.5 on min setting, 8.5 -auto, 6.9 -max. The same readings on both regulators old and new one, when old one fitted fan not working at all with new one fan works on full speed constantly

 

[television]

I think the new one is faulty, the only voltage in goes onto 1 terminal, another terminal drives the motor, 1 ground and the other from the control unit

The circuit and connections are here

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1993/400E/SYSTEM WIRING DIAGRAMS/4628.pdf

 

[iwona]

Will buy new one then, any suggestions? Should it be good quality pre -owned or cheaper alternative, found one -made in Germany for £80, MB quoted £360+VAT for new

 

[television]

they are often on Ebay cheap,, surely MB cannot charge that much

 

[Frontstep]

Do you have a part number to post ?

 

[iwona]

Bosch part number 9 140 010 099

 

[WG M-B]

Why don't you try a second hand one? Or even ecp if money is an issue? I was told not to buy them off ecp but tried one and it has so far worked perfectly for three+ years!!!

 

[Frontstep]

If you look on the American forums there is quite a lot of discussion on this particular part.
It kept coming up when I was reading about the blower resistor problems.