Hello, My car is a 97 sl500. I've been struggling for months with random electrical gremlins. The radiator, oil level and windscreen washer level lights will flicker accompanied by the Tach needle dropping, but no miss in the engine. Occasionally (but never without the flickering) the transmission will lock into whatever gear it was in, and shifting from park slams hard into gear. Usually this corrects itself on restart. Diagnostics show a shopping list of faults that keep changing, but CAN bus failures keep coming up. Recently I discovered that the ebox cooling fan does not run so I'm guessing that the ecu is overheating. The fan works when 12V is provided directly so its not that. The strange part is the fan has red and brown wires, but they are plugged into brown and yellow/blue wires that go to the module in the control box that has the three fuses on top. There is no power coming from this wire at any time. There is a lot of evidence of the PO having done wiring work, so I'm wondering if he plugged the fan into the wrong connector. Can anybody tell me where the fan gets its power from? Everything else works perfectly. Thanks, Craig

The fan is powered by pin 19 from the base module blue/yellow wire thats the one with fuses on top in right module box.The fan is turned on at engine rpm of 1500 or greater or 55c.The module box fan ,trans control unit,cluster idiot lights get power from circuit 87 which is fed by that base module.Fuse f2 on the module 10 amp.From the base module pin 27 a red and black wire circuit 87 runs to a 6 pole connection block to distribute power,its near the modules in right rear of the engine compartment to the left of the module box.The ground for the base module is near right fender in front of the module box make sure its not loose

Hi Benztech, thanks for the detailed reply. At least now I know the wiring is correct. Checked out the module today, fuses are good but no power through the yellow/blue wire at any rpm or temp. Checked grounds and the connections at the 6 pole connector, all seem fine. Funny that it seems that in most models the fan runs all the time the ignition is on. Wonder why the SL only cools the ecu at certain times. Still, the fact that my fan never runs could mean the ecu is overheating and could explain random electrical faults. Hope this doesn't mean I need to replace the base module. I'm considering adding a second fan hooked up to a constant 12V and see if the problem goes away. By the way, any idea where this module get its temp. information from?
Thanks again
Craig