Fan circuitry is usually on the board, not the fan. The Yellow wire is part of the speed Dell mounted a thermistor in the fans flow, but the speed control was on the board. Many other (computer) fans simply have a Tachometer to report slow or stopped. First Question: How many wires to the fan?
The link at the end was the useful part. No where in the product description does it state either way on the fan running all the time, but several of the reviews stated that it does run all the time and is quite noisy.
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