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benzboy 03-10-2000 10:14 PM

hello, i am working on a mercedes 300e 1988

with a 124c chaisis. the porbe is that the fan blower stays on all the time when the ignition is on. i am thinking its the blower motor regulator. what u think? if u think is is the blower motor regulator the please tell me where it is and how long it takes to do a job like that


stevebfl 03-10-2000 10:43 PM

The regulator is in the blower housing at the base of the windshield. Its probably about a two hour job by the book.

There is external access to the circuit. What you would be looking for is a 1-4v signal from the pushbutton control unit. I don't remember the color, email if you would like a diagram.


[This message has been edited by Webmaster (edited 03-14-2000).]

Benzmac 03-11-2000 09:17 PM

I have never seen a regulator fail in this way. Most likely you have a faulty circuit in the pushbutton control unit.

1981 280GE SWB
1987 16V

jeffsr 03-12-2000 09:19 AM

I believe there a NTC switch on the head that controls the aux fan. I'm not sure where that switch sits in the control circuit. I believe it has only 1 conductor. Check it with reference to ground with the engine cold. Should show open circuit.

Jeff L
1987 300e
1989 300e
1987 BMW 325

benzboy 03-12-2000 08:58 PM

the benz i romoved all the switch and un plugged them and everything but still the fan stay on. but when i unplug the regulator it stops

benzboy 03-12-2000 09:02 PM

please e-mail me the diagram please.

[This message has been edited by Webmaster (edited 03-14-2000).]

stevebfl 03-12-2000 09:54 PM

Some of the answers have me confused. Are we talking about the blower that blows cold air in our face or the blower for auxiliary cooling (in front of the radiator)?

The fan for comfort is powered by a transistorized regulator. The basic circuit has three wires. Power, ground and control signal. The control signal is a 1-4v signal that comes from the pushbutton control unit. These three wires are all that makes the blower go. The control signal wire is easy to get to under the hood at (I think) a three wire connector on the firewall. (I will refresh my memory in the shop tomorrow). The actual regulator I think has 5 wires (including the output to the blower through the regulator).

Disconnecting the signal wire should shut-off the blower. I also have never seen a regulator fail in this manner(leaving the fan on all the time). I presume you have some voltage at the signal wire all the time; either that or you have been talking about the aux cooling fan and I'm all wet.

If you need a wiring diagram write me at work

Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by Webmaster (edited 03-14-2000).]

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