I jumpered the pigtails on the red pressure switch (the one I originally thought was the temperature switch) and I could hear the relay clicking. When I started the engine and jumpered the wires, the low speed fans came on. So, it looks like the wiring is correct. Now, I just have to contend with the less-than-adequate cooling at idle. Thanks again.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles