[header] How to test a fan clutch [title] Pay attention to changes in air temperature. [step] One of the most common symptoms of a fan clutch on the outs is an inability to properly cool the air circulating through the vehicle. Switch on the a/c and turn it down to the coldest setting. 
If it fails to cool down after several minutes, or seems to be emitting unusually warm air, there could be a problem. [substeps] Hold your hand a few inches away from the vent so slight variations in temperature will be more noticeable.