Erratic electric fan operation can also point to a plugged radiator, which can be a bit tougher to diagnose. Plugged radiators will have hot and cool spots in the core. having a fan on the front and back of the 124 radiator makes it almost impossible to tell if that is what's happening. Test for electrical gremlins first, but don't rule out a bad radiator.

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Fourings

84 Audi Coupe GT with Turbo engine, EFI (buh-bye CIS), Jamex seats, Koni's/H&R's, e-code lights. 210k and counting.
1992 Anthracite 400E, 161k, "Grey Ghost".
1986 VW Quantum Syncro, 192k, gone to the crusher in the sky.
1989 300TE 172k. (Was mine, now also Mom's car)
72 280SE 4.5 (Mom's car)