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 firstname.lastname@example.org
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by Webmaster (edited 03-14-2000).]