Locating Fan switches
 

I have a 1988 190e 2.3 and am trying to lacate the mechanical fan switch and electrical fan switch.

on my car they are located on the front of the engine near the thermostat. One is in front of the other, one has three wires and two prongs, the other has two wires and two prongs. Because each has two prongs, they could be interchanged, the plugs are identical.

I shorted each one, one starts the mechanical fan driven buy the belt, the other starts the 2 stage electrical cooling fan in the of the radiator and ac coil.

I want to make sure that these are plugged into the right sockets.

Is the switch in front supposed to contol the electrical fan and the one in back supposed to control the mechanical fan or is it vice versa?

Unless I'm mistaken, and that's a very real possibility, the mechanical fan is switched on and off mechanically by an integral clutch. I believe one of the two temperature switches you are referring to controls the aux cooling fan and the other provides engine temperature data for the computer.

I don't know which plug goes to which sensor, but hopefully someone who does know will chime in.

400E, the 2.3 has the electrical clutch for the engine fan, unlike just about everything else in that era, which had the visco fan clutch you're thinking of. Too late for me to look it up right now, but it does seem to me that on the water pump itself, there is a sensor that screws in, has only 1 pin, provides a ground for something, I'm thinking this was for the aux fans (electric fans) in an over-heat situation (high speed fan activation).
I would think you could get a fairly good idea if the two sensors you are talking about are correct just by how the wire lays if you tried to reverse them.
Gilly

Very interesting! You always learn something new on this list. That's the first I've ever heard of an electrically-controlled mechanical fan. Leave it to MB ...