Could be the clutch, but likely the thermo-switch. Wiring varies per year/model, but with ours (1991 2.3) it is the 3 terminal unit behind the thermostat housing. Again with ours, shorting the contacts together in the 2-terminal socket connector while the engine is running clutches in the fan, verifying the clutch itself is good.

Replacing the switch involves removing two other thermo-sensors first. This caused no coolant loss since they are located at the high point of the coolant path. Of course, cool down and depressurize first.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7