89 Tempo cooling (radiator) question

My daughter has an '89 Tempo, on which the radiator cooling fan has stopped working. The Haynes service manual says that there are three different components involved with this circuit:
- Cooling Fan Control Module (inside glovebox)
- Radiator Fan Control Relay (inside engine compartment, next to left headlight)
- Coolant Temp Sensor (on housing near thermostat)
My question is, which one of these is *most* likely to be bad? I'm asking because the first item is $48.00, the second is $50.00, and the third is about $18.00. The manual doesn't show how to test any of these components, and I don't want to replace a working component (since they can't be returned once purchased). And, I don't want to spend over $100 to replace all three if two of 'em don't need to be replaced.
Any advice appreciated!!! Thanks......
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The fan motor or the wiring to the fan might be bad as well.

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Just replace all of them and stop trying to save a couple of dollars.

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