I understand that the electric rad fan in my W123's is actuated by the AC system only. The temperature switch on the filter/drier turns it's relay on above some temperature (40 C?, forgot exactly, I tested some spares and wrote value on them). It definitely helps since when I had a bad temp switch the AC barely worked at idle on a 110 F day (sat 2 hr in jam). If working, the filter/drier should not be too hot to comfortably touch. The relay is under the plastic box on the driver's inner fender (another relay for AC clutch too unless an 85 CA). Rollguy has a post rigging the fan to always come on when the AC clutch engages, but even at highway speeds where it isn't needed.

The fan would surely help engine cooling if you could actuate it to also come on with radiator temperature, though it is a bit wimpy for that world. Hot-rodders who sometimes must live w/ an electric-only rad fan like the 2-spd Ford fan used in Taurus etc. Once driving 30 mph, you don't need a fan.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans